To assign all favorite letters to a disk drive (or) part of (or) a volume for the first time do as said below. First start log in as user.
1. Then click start=> control panel option, it will list sum of option then select Performance and Maintenance. (Note: This option will be enable only on control panel. So we should open it.)
2. Now click Administrative tools and then double click on computer management. Now some of option listed on the left side of it then selects Disk management.)
3. Now right click on the drive, as you want to create letters, and then click on change drive letter and paths.
4. From that click Add
5. Now default computer mark the type of letter from “Assign the following drive letter” Now you can make changes only by selecting some other type of letter.
We see how to change the type of letter for a drive on its parts
1. Select start=>control panel a window will be open then select “Performance and Maintenance” from that window.
2. Now click on “Administrative Tools” after that double click on computer management. Now you get sum of option from the left side of window here we select the Disk management.
3. Right click on the drive (or) the part on we want change the letter type after that select “change drive letter and paths” from it.
4. Now click on “change” option carefully
5.Now select the type of letter from “Assign the following drive letter” option and give ok to it
6. Carefully give yes when a dialogue box open with the message of whether change the type of letter. Now you got to selected letter types enabled on the drives.
To change the already existing letter, use following
1. Click start=>control panel. Now you get new window. Select performance and maintenance option from that window.
2. Now click on Administrative tools after that double click on computer management. Now select the disk management option from the left side of the window.
3. Right click on the drive (or) part as you want to change the letter type, then “change drive letter and paths”
4. Now carefully click the “remove” option
5. Now you got a dialogue box, which contains the warning message. Click Yes on it. At this time you got the certain type of letter will be removed.

Like this you would apply this option for your drive.
Thanxxx