Reliablity of COPY on XP via FlashDrives

[Walt43]

I plugged in two USB FlashDrives into XP.
Both had been formated on this XP and then put data on them. One was a 4GB, FAT formated for my W98SE, AT machine. The other was a 16GB, NTFS formated for use between the XP and a VISA Laptop. My only Internet is the VISTA.
I mistakenly allowed the XP to do a ScanDisk /with fix and a Defrag on the 4GB, Fat Flashdrive.
Is this legal? Did I trash the data? I thought things were fine untill I discovered some bad checksums.
With the two USB FlashDrives in XP, I did a "COPY" the entire 4GB to an empty folder on the 16GB. And begin to find bad checksums in the "Copied" data.
I used MemTest86 on this XP an it passed fine.
Help?

[Geek-9pm]

Personally I never  had that exact problem.
My problem has always been the cheap flash chips I got off eBay.
All of the brand name stuff is good, IMHO.
An I use Windows XP a lot.

[Walt43]

Personally I never  had that exact problem.
An I use Windows XP a lot.

Would it be too much for some experieanced person to do such a test for this thread?
The 4G FD is a Walmart bought "PNY", formatted to FAT, used between W9X and XP and VISTA.
And the 16G FD is walmart bought, "SanDisk", formated NTFS. Used between XP and VISTA Laptop.
Such would help me to know more how I got there and more about how I can get out.
Thank you for your reponse.