IS YOUR PEN DRIVE NOT DETECTING THEN TRY THE FOLLOWING COMMANDS IN COMMAND PROMPT AND MAKE YOU R PEN DRIVE WORK............. 
1> commands

Open the DOS prompt (Start >> Run >> cmd)
Type:
FORMAT X: /FS:FAT32 /Q /V:PenDrive

This will reformat the Pen drive, using the FAT32 file system, and label the drive PenDrive. Replace X: with the actual drive letter of your Pen Drive.
For more help on this       command, type:
FORMAT /?
In the above command
X specifies "Force the volume dismount if necessary"
Q specifies "Quick format"
V specifies "Volume label"

2> Format
E: /FS:FAT32 (where E: is my pen drive name and FAT32 is the fle system I want on the disk)