PNY Optima Attache 4G flash does not work

Hello,

I bought a PNY Optima Attache 4G u-disk. It works on my desktop and some other computers, but not on my laptop (Dell Latitude D630, Windows XP). When I plug the u-disk, the light on the u-disk flashes, then nothing happens. Sometimes I can see the u-disk from my computer, but the access to the u-disk is extremely slow. In other words, I still can't use it.

I checked PNY website and google online and did not see any solutions. The website says it does not need a driver. But does anybody know why I can't use it with my laptop?

Thanks.