cruzer memory stick problem

I bought a 512MB Cruzer memory stick to back up files while trying to fix problems with
my computer. I transferred a large number of files to the memory stick. Later I tried to retrieve these files on a number of computers and the memory stick is not recognized. I tried a different memory stick and that one is recognized ok. If the stick is defective (don't know if this is the case) how can I find this out and can I salvage the files, since I deleted the originals. BTW, I have two 512MB stick that are not working.

Thanks in advance for any hints.

Could possibly be one of two things:

1) The computers you are trying to transfer to are not USB plug and play compatible. The cruizers should have come with a driver/installation disk. Try installing the drivers onto the system before putting in the drive.

2) I've only heard of this, never seen it happen, but apparently it is true. When you transferred the files from the computer, how did you unplug the drive. Apparently with some usb drives, if you simply unplug the drive without using the "safely remove hardware" utility, you can erase or corrupt the data on the drive. If this is what happened than you are just about out of luck.

I tried downloading the driver, but I have XP and the Scandisk
site says a driver is not needed. I am afraid it may be the 2) option.
Thanks for the input.

dmeer