If you can't get into windows tabormeister's way, you may have a corrupted hard drive, or other problems. Try burning a linux live disk (Fedora 12, or Ubuntu 9) and boot of the disk, you will need to download an ISO image, and burn it to a CD or DVD (Just Google "Linux ISO's" and look for a fedora or ubuntu ISO(these versions of linux are the most user friendly) entitled "[OS Name][ Version #]-i686-Live" and download and burn that to a disk(Almost all distrobutions of linux are free).
Now, put the disk in your laptop, reboot it, and set it to boot from a CD in the Bios (It may already be set) and select "Boot"from the linix menue (Not Install!) and it should load into a desktop that looks a little like mac os.
Now, go to the menu (Top Left on toolbar) and navigate to the"Disk Utility menu (or somthing of that similar name it's different in each os) if the utility can find the disk, and if it is readable (Don't Choose to mount it!) then windows is corrupted, you can try to buy a second drive, install it in the laptop, remove the old one, and put it in a usb 2.5" drive enclosure if you want to save your files, just install xp again on the new drive. OR if you don't care about your files, just reinstall on the old drive (but then they can't be recovered).
If you put your old drive in an enclosure, than you can connect it to your computer at a later time, and copy your old files to your new hard drive.