How to assign a letter to the drive in command prompt of vista

Hello,
i wanted to restore my system, dv 5 pavillion back to factory setting using system recovery but it formatted and restarted to install the OS,it got to cmd.exe -startnet.cmd and kept on restarting to that point and when I entered to command prompt to install with this command;
x:\sources\recovery\en-us\recenv.exe.
it got to a point and complained that drive letter is not compactible with all the os features and now ask me to assign the drive letter. but when i check through the command prompt I saw drive d: and f: f-recovery partition