Q: Wet-sanding uses decreasing levels of abrasion to scrub away and buff smooth a clouded plastic surface. There are many variations of this method when it comes to cleaning car headlamp covers, since oxidation can cause clouding that may reduce the effective brightness of your headlights. Clean the surface of the plastic item first with a gentle soap, soft cloth, and clean water. Protect any surrounding surfaces (e.g., car paint or chrome around your headlamp covers) with thick layers of painter's tape, or even taped-down plastic sheeting. Soak the sandpaper in clean water, or spray it down while working. Keep the plastic damp as well. Use firm and even, but not excessive, pressure. Rinse and check the surface for even abrasion when switching sandpaper grades. For a more aggressive application on, for instance, a car headlamp cover, you could use 400, 600, and 2000-grit sandpaper. To exert greater caution with your headlamp covers (or with something like a boat windscreen), try using 1000, 1500, 2000, 2500, and finally 3000-grit sandpaper. After thoroughly rinsing the item and drying it with a soft, lint-free cloth, apply a commercial polishing compound to fine-tune the abrasion process. Follow the instructions provided with the product, but expect to go very slowly so that you can methodically work the compound over the plastic item. Look for abrasive polishing compounds for plastics at auto parts or marine retailers. If your plastic item doesn't require this level of care, you can opt to simply wipe rubbing alcohol over the rinsed plastic in order to remove any lingering dust, oils, or residue. Unfortunately, once you've done all this work to make your plastic crystal clear, the yellowing and clouding process will begin again immediately. If you want to add some more time before you have to wet-sand the plastic item again, consider applying UV protection to hinder the impact of ultraviolet light. For automobile headlamp covers, for instance, you could apply a paste wax intended to provide UV protection. Or, you could use a UV protectant clear-coat spray. If so, work slowly (according to the product instructions) and be sure to fully cover any areas (car paint, etc.) that you don't want the clear-coat to get on.
A: Use dampened sandpaper on wetted-down clear plastic. Scrub in a circular motion with progressively finer grades of sandpaper. Apply an abrasive polishing compound to smooth out the plastic. Apply a UV protective coating to slow down subsequent clouding.

Q: This might help your PC performance so you can avoid formatting. You may also consider re-installing Windows XP. If you are trying to eradicate a virus, this will not remove all the files. The virus may still be present after re-installing. Most brand name manufacturers include a disk that can restore your computer to the state it was the day you purchased it. Some only include a Windows XP disk, and some provide nothing at all. If you have a restore-disk you can save yourself from having to reformat your computer. Once you begin the process you will not be able to access files on your computer or the web. If you have a printed copy of the necessary steps and troubleshooting procedures you will be able to reference them as needed. All important data should be backed up before starting this procedure. Remember that all hard disk data will be lost when you reformat. Check out this article on how to backup your data in Windows XP. Ensure that you save that backup to a CD, thumb drive, or external drive. Note whether you have the software CDs to extra devices such as printers or software you may have purchased. If you downloaded them, then ensure that you either can re-download them or backup those files so you are able to re-install them after you reformat your computer. You may also want to note the make and model of your devices. You can find these by searching for "device manager" from the start menu. Once inside the Device Manager, you can click on each category to see what devices are installed.
A:
Consider defragging or using an anti-malware program first. Check to see if your PC manufacturer included a restore-disk. Write down or print out all instructions you need to reformat. Back up your data.