I have transcend 4GB pen drive. when i insert my pen drive in system it shows the removable disk icon in MyComputer window . when i click the removable disk it shows 'please insert disk' ...i cant open the pen drive window ... i cant do format also... please help me to over come this problem...

Hello, from my understanding, such pen drive problems could be caused by RAW file system error and virus infection, etc. as with yours, merely go see whether this flash drive is also displayed as RAW file system in Properties. If so, with important data reserved on this RAW flash drive, merely download RAW format USB Thumb drive data recovery software to take everything desired back. And then format it to convert RAW to NTFS.
But, if you only find it is shows 0 bytes used space and 0 bytes free space, go check whether it is virus infected.
Hope these words are not too late for you.

Try the following link for a utility to help you out.
http://www.freedownloadscenter.com/live/how-to-format-transcend-pen-drive/drive.html