Slow transfer rates to thumbdrive

I have an 8gig Duracell thumbdrive, to which i wanted to copy a 6.55 gig video file . First I had to re-format the thumbdrive from FAT32 to NTSC before i could even BEGIN the transfer, then once I started the transfer I watched in disappointment as - at first, the data transfer speed was well over 100Mb/sec . This rate RAPIDLY decreased to about 10Mb/sec . It took quite a while to transfer the one single file to the thumbdrive. After Googling around, I have noticed there is some confusion on the issue, and that I'm not really sure what to believe. Does anyone know why my data transfer rate would so rapidly drop from well over 100Mb/sec to around 10Mb/sec ? It appears to be an issue with Windows 7 (which i have) and Vista, but not with XP or Linux .
I'll Google around a bit more and see if I can find some information that appears to be credible.

 

I'm ok at math but how long did it take to write the whole file to USB when all was said and done?

Under ten minutes and nothing to worry about. (fragmentation of the original file could be a major factor) 45 minutes and you have a problem.

 

It was more than 20 minutes .