You should use an anti-virus full time. "Microsoft security essentials" is free (google it) and runs on XP. Have it do a full scan of your system before you do anything else.
Now, before other repair actions do a full backup of your current system to an external USB drive. XP professional has backup, but the other versions don't so you may need to buy a utility like 'acronis' or maybe HP has an installed backup utility. Then explicitly move any files you know you want (music, photos, copy of registry, etc.) to the USB drive. Then unplug the USB drive. Do not plug it back in. Fighting virus damage sometimes spirals into total system software fails which would force you to format/wipe the disk and lose data. Do not plug it into another computer unless your are SURE that the computer has up to date antivirus protection, you may have backed up active viruses to the usb drive.
A virus does a lot of damage, some intentional and some by accident based on bugs in the virus. You can download a new copy of IE from Microsoft (google will find that too) to replace the quarantined one. If there are any other files in quarantine then google their names, find out what they are part of and download and reinstall.
You can try the standard recovery once you have a safe copy of your data. I haven't used the HP standard recovery before. There are some notes about where your data goes that make me think its doing more than just reinstalling windows.
http://h10025.www1.hp.com/ewfrf/wc/document?cc=us&lc=en&docname=bph07145#N79
http://h10025.www1.hp.com/ewfrf/wc/document?docname=c00276693&lc=en&cc=us&dlc=en
-skip the rest if you don't need a full system recovery-
If the standard restore leaves your system unstable, or if you just decide to skip to the full, destructive restore then good. This has the side benefit of fixing all the registry edits you've done and getting rid of all the debris that a system accumulates. However, A FULL SYSTEM RECOVERY kills everything back to original. All your photos, installed games, music, bookmarks, etc will be lost.
I've done HP full installs a number of times. You MUST get rid of any USB attached devices other than mouse and keyboard. If you've swapped video cards there is a chance that the recovery will fail. If necessary swap back in the old video card (doesn't amke sense, but I've had recovery fail on a new card, work on old). Remove any PCI cards (network adapters, sound, raid controllers, etc. ) that were not in the initial configuration. Ypu've already burned a set of CD/DVD recovery media. Make a second set after you do full recovery (the system forgets about the first set when you do a full recovery).
Once you do the full system recovery you must repetitively call windows update and reboot. Each time you call win update it'll load a new set of compatible changes. When you reboot you complete install of these changes and allow windows to install the next set. It can take hours on a fast connection to get back to current. Then make sure you have your antivirus running before you do anything else.
Once you are service current and running an anti-virus it's relatively safe to plug the USB drive in. Have your antivirus run a full/deep scan of the attached USB drive. Then start transferring over your files.