Sounds like it could be a virus, trojan or some other type of invasion. However if you received notice of a hard drive warning, then I would just go with the new drive. These warnings are real.

If you have XP, and can afford a new computer, I would opt for a new computer with Win7 64. XP is good, Win7 is better.

If you already have Win7, then I would try restoring from your system image repair disk...that is if you actually made an image system repair disk in the past. (It's quick and simple in Win7). If you did not make such a disk , then other options would be; try a restore, or one (or more) of the many free programs available to 'clean' your hard drive. Among others, a few of my favorite such free programs are Advance System Care, CCleaner and ATF Cleaner

You can try these, won't hurt, but IMHO, it's the hard drive, and if your satisfied with your computer, and system, a new hard drive is the way to go. If you are ADDING a hard drive, and keeping the old in the same laptop, then I highly recommend Western Digital, and the free Acronis WD Edition for a fast, easy way to clone, backup, add a new hard drive, and more.

Good Luck