Beware! I have an old Toshiba Lap Top that came with a 15 Gig hard drive. I tried to buy a larger hard drive for that computer from an online hard drive web site. They claimed that they had a 100 Gig HD that was compatible with my computer. When I received it I tried to install it. It wouldn't fit. I noticed that pin configuration on the new drive was totally different from the old drive. The online merchant kept insisting that the drive was, in fact compatible, and I was installing it wrong. Finally, after three weeks, they finally agreed to take back their drive.
A few months later I tried the same thing with another online HD merchant. The results were more or less the same.
The best thing to do is to go to the IBM web site, and see if an upgrade is available. That is the only way to know, for a fact if a larger, or replacement drive is available for your lap top.