What I would do is:
If you have a floppy drive, insert a Windows98 Startup disc in it (or if you don't have one, look it up on line...you can download the files, no problem...best ones are the ones that don't use any of your HDD for the boot process and enable your CDrom at the same time), then Fdisk and delete the partition(s) and format to the largest capacity. Next, shut your laptop down and put your WindowsXP bootable CD in and let it do its stuff. It will also re-format, but this time in NTFS or FAT32 (if you prefer). This is a for-sure way that the XP CD uses all of your HD and doesn't try to make a separate partition, but if there was a service partition on your HD it will probably delete it.
After you install Windows, go into your Device Manager and you'll see what drivers are missing. Then, go to Bill's page (
www.thinkpads.com), not this forum and find the Drivers Matrix link about 3/4 way down on the right, double click on it to get to IBM's site where you'll find all of the drivers and update files you'll need. I recommend you do this with a broadband connection and not a dial-up, as it will take some time otherwise.
You'll also want to do Windows Update (but if any drivers are listed to update their, ignore them...you only want to update drivers from IBM itself). Also, don't forget to put Antivirus and Anti-spam/adware program on your Thinkpad...to me, these are essential.