Critical Error on Reboot - Could not find Registry

This is my first Dell Dimension 8300..I have bought everybody in my family a Dell but this is my first.

Pentium 4 - Windows XP Pro

I received the computer on Monday and it has crashed 2 times already.  I know I am a jinks but the Micron PC I have been running for the past 4 years has not crashed that many times.

The computer started slowing down the 2nd day I was using it.  The first thing I did was start uninstalling all that junk that was installed that I do not use.  AOL, Earthlink, etc.

I prefer a computer to be loaded with the Operating System, and only what I request nothing else. I like it to be as clean as possible as I am a jinks.

I rebooted this morning and Windows XP would not come up.  After about 5 minutes, I got the blue screen and the message that the Registry is corrupt or missing and it could not load.

I do not know how I got it up.  I went to the Bios.  Changed Bios so it would boot to CD Rom.

When it finally came up, it reported that it had recovered from a serious critical error.

When I uninstalled all this junk, I did a scandisk and defrag and there are 2 fragmented files in the MFT.

But I am not sure that is the problem.

I would appreciate help.  I thought I would have to do a clean install this morning.  I can do that on my old computer but I do not know how to do that on a Dell and I must say I should not need to since it is brand new.