That sounds like a very weird problem.
This is a complete stab in the dark -- games that use .ogg sounds run extremely slow if the .ogg codec isn't installed. That can be found here --
http://www.vorbis.com/Of course, I have no idea if the games you tried use .ogg sounds, nor if it could be connected to the flash-drive thing (perhaps you have codecs on the flash drive? I honestly have no idea how codecs work).
But that has historically been a common reason for GS games to run really slowly when they shouldn't.
Jibb