My computer is a Compaq Presario 6 yrs old and experiencing a number of problems. How to I clean it up and start from scratch - as it was set when I purchased it?

Number of USB 2.0 Ports - 6 http://www.amazon.com/Compaq-Presario-Desktop-2-53-GHz-Pentium/dp/B00008LUOH shows there are 6- 2.0 USB ports see here.

Hello, you are experiencing this because of the Boot priority setting in your bios. Your computer has been set to boot from your hard disk first and so it will never try to boot from a CD when it starts. There are 2 ways to fix this:
1. Go into your bios (usually by pressing F2, F10 or Delete key as your computer starts) and set the boot priority to check CD or optical drives first. Consult your PC manual if necessary.
2. Press F12 when your computer starts, this will bring up a menu to select boot options. Choose your CD drive.
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Well, here's the bad news. 1) Windows XP is not supported any more by Microsoft. (2) You need the original CD's that previously installed XP on your computer. If you can't get them from the previous owner, then you'll have to try and find some original CD's and reinstall XP on your machine, from scratch. (3) If your computer has what it needs, an option is to install Windows 7 on your computer - it depends how old your computer is and if it has the necessary hardware.

It looks like you can replace the mobo for $120 - $190.

First thing to do if you have not cleaned the inside of the computer is give it a good cleaning. There may be enough dust inside that it is overheating. Reply if that is not the problem.

Here is what I mean. You don't have to get one here, but here are what they look like.

http://www.tigerdirect.com/applications/category/category_slc.asp?CatId=2779&name=3.5-Enclosure-IDE&Nav=|c:2778|&Sort=0&Recs=10

Often you can blow the dust out of the fans and it will help. In your case the bearings have most likely dried up on a fan. First blow the dust out of all the fans. To find the offending fan you will have to block the blades with something. Once the fan is found you can either replace it with a fan of the same size or re-oil the bearings. To re-oil, carefully peal away the label on the fan. There might be a plastic plug over the bearing, carefully remove it. Drop a few drops of 4-in-1 oil or sewing machine oil into the bearing. Stick the label back on and put the fan back into the system. It should be much quieter now.

At this point, you can try to clean your disk # 4 and see what happen,
or try to make a copy of disk # 4 (if you can copy the disk) and try again.

or

1) Contact your customer support and ask for a new set of disks.(or only # 4)

or

2) Boot your computer with another OS disk (win XP)

or

3) Boot your computer with some utility disk

have you tried your power options, you might have it set up wrong

yep! you shud try to clean you dvd rom.. you can use a dvd rom cleaning kit by running it on the optical drive.