Portable Harddrive - Works on Newish Lappy, not on... Got a portable harddrive, PCMIA card USB

Question

Got a portable harddrive, PCMIA card USB 2.0 adaptor and the power lead for pcmia card. Drive has enough power, but is not recognised in my computer (running XP). The drive works fine on my desktop and my 3 yr old laptop. The laptop I am trying it on is a IBM Thinkpad X20 - 2001 I think. It only has 64 RAM, waiting on a 256 RAM stick to arrive if that will help.