Permanently erasing data and recovering 'deleted' files

The technology behind the products -

Let us check it out w.r.t the FAT32 file system. The FAT file system is so called because of a 'File Allocation Table', 2 copies of which are stored on the HDD immediately after the MBR and the Boot Record. Theoritically speaking, files are stored as clusters on a HDD (where a cluster is, a group of sectors). The different clusters of a file need not neccessarily be contiguous. The FAT table contains 32 bit entries, each entry corresponding to a cluster on the HDD. NOTE - Of the 32 bits in a FAT32 table entry, only 28 are used at present. This entry size of 28 also acts as a limiter for the maximum no. of clusters possible on a HDD (which will be 2 to the power 28). When a command to read a file is given, the OS locates its first cluster from the file's directory entry. It then checks the FAT table entry corresponding to that cluster. That entry carries the number of the next cluster of the file...so on and so forth. Some entries in the FAT table, might carry special code to indicate that -
(1) The cluster is free.
(2) The cluster contains one or more sectors which are bad and hence, the cluster should not be used.
(3) The cluster is the final cluster of the file.

So, what actually happens when you 'delete' a file?
The entries in the FAT table are replaced with special blank entries to indicate that the particular cluster is free for use. The actual clusters which contained the file data would still be there, until they get over-written by the clusters of another file.

What happens when you 'format' a drive?
The FAT table is written afresh on the HDD. NOTE - Once again, formatting a drive does NOT over-write the actual clusters that carried the file data.

This is the idea exploited by the file recovery programs. If they can locate the actual clusters of a file BEFORE they get over-written by another file's data... the old file can be recovered. This can be done in several ways, for example, by restoring the FAT table from its backup copy. NOTE - You will remarkably increase ur chances of recovering a deleted file, if u refrain from any disk activity after the file was mistakenly deleted (like disk defragmentation, new file creation, moving files around). In fact, most of the file recovery programs, work from CDs / floppy disks so as to prevent the possibility of their setup files over-writing the files that u deleted from the hard drive.
The PERMANENTLY erasing programs, on the contrary, work by over-writing the concerned file's clusters with a random sequence of 0s and 1s to permanetly erase the prev. file's clusters. They might also carry out several passes of this process to ensure that the files are indeed deleted permanently.

The FAT table is known as 'Master File Table' (MFT) in case of NTFS file system.

A freeware to PERMANENTLY erase data -
Sure Delete - http://www.pcworld.com/downloads/file_description/0,fid,22393,00.asp

A freeware to recover deleted data -
PC Inspector File Recovery -
http://www.pcinspector.de/download.asp?language=1#file_recovery
Restoration - http://www.geocities.jp/br_kato/

Reference URLs -
http://aumha.org/a/recover.php
http://en.wikipedia.org/wiki/File_Allocation_Table

SnipURL

SnipURL (www.snipurl.com) -

Is primarily an easy way to shorten long URLs. This makes it easier to share web addresses with family and friends.

Some of its features :
1. Can be added to the Links bar in the browser to easily shorten the URL for the page you currently are at.
2. Once you register on this website, you can access ALL your 'snipped' URLs together, edit them and create more meaningful URLs. You can also keep a track of the no. of times a particular URLs has been accessed.
3. A snipping once created is PERMANENT. So, you can keep on sharing it again and again.

NOTE - Unlike as claimed by the SnipURL team, the system I worked on, did NOT allow me to create a SNIP IT button on my IE Links bar, by simply dragging the 'Snip this' option on their home page to the Links bar. As a workaround, here's what I had to do -
(a) Open ANY web page in the browser.
(b) Add that web page to the Links bar in my browser.
(c) Edit the targetted URL for that Links bar button to point it to the javascipt code pointed at by the 'snip this' option on the snipURL home page.
Evidently, the SnipURL team IS aware of this problem, they too have some suggestions at -
http://snipurl.com/faq to deal with it.

For more information about SnipURL check out their features page at -
http://snipurl.com/features

Another service of the same kind would be TinyURL (www.tinyurl.com).

Daisy chaining in USB

Never really paid that much thought to it... until today, at least.

What is daisy chaining w.r.t the USB bus standard?

Daisy chaining can be depicted as -

USB port on computer --- USB device --- USB device --- .... ---- Terminator

It has also been very aptly defined in the 'daisy chaining' wiki @
http://en.wikipedia.org/wiki/Daisy_chain

USB standard says that you can have upto 127 devices attached per USB port in a daisychain. But then, it also puts a limit on the maximum number of hops permitted. This limit is FAR lesser than the 127 devices that can be connected per USB port. So, the question is how do we explain this contradiction? Simple, we daisy chain POWERED USB hubs and each of these powered hubs is allowed to carry multiple USB devices. This has been better depicted in the image on the left.

NOTE - If tomorrow, you choose to attach two USB hubs to a single USB hub, in turn connected to a single USB port on the computer, the resultant network will be said to have a 'Star topology'. It WON'T be a daisychain.

This concept will be equally valid for the Firewire standard. The only difference is that it allows upto 16 hops and 63 devices per Firewire port.

Password in Microsoft Outlook mailbox

How to stop prying Toms from accessing ur Exchange server based Microsoft Outlook mailbox, if u r gonna leave ur workstations unattended for some time?

(Technical subject : How to make Microsoft Outlook (w.r.t Outlook 2002, in this case) prompt u for a password and NOT logon automatically using the NT login information?)

Click on Tools > Email Accounts.
Choose the option "View OR change existing email accounts".
Doubleclick the Exchange Server account in the E-mail accounts window.
In the Exchange Server settings window, click on the More Settings button.
Click on the Advanced tab.
In the Logon Network Security drop box, choose None.
Click on Apply and navigate through the rest of the panes (You might be promoted to enter the NT Login information once... enter it.)
The next time u open up the Outlook mailbox, it will display your NT login name AND the DOMAIN name and will prompt u to put in the NT password to proceed further.

IE Links bar

This one might seem an easy one for some. For others, it will be another thing to add to their already burgeoning knowledge-base -

The Links bar in IE :
It is an easy way to remember some site URLs and have them display as easily accessible buttons in the IE window.
To display the Links bar, go to View > Toolbars and check the Links option.
To add websites to the Links bar, choose Favorites > Add to favorites and ADD to the Links folder in there.
To remove the Links folder from view in the IE Favorites menu, right click on Links, choose Properties and SET the 'Hidden' attribute. If u try to delete this folder, it will be created again and again (you have to use a registy setting to remove it permanently.)
To export the URLs in the Links folder to a file (so that they can be imported onto another machine), just EXPORT the favorites. Links URLs are also a part of Favorites, remember.

REF URL - http://www.i-t-w.com/pages/articles/IE_links.html