if by chance dell gave you a winxp cd ,you can boot to it and do a "R" for repair and at the prompt type in , chkdsk /f

if you don't have xp cd you could get xp boot floppy set from microsoft and use them .
http://support.microsoft.com/?kbid=310994

this is most like caused by the windows updates ,making change to a device file or .dll file that something like the video device was using

Oh jesus, sounds like you got the curse of the "updated." Once you get this back up and running according to caperjack's instructions (which should, by all means, work) just upgrade it to the March release of XP Service Pack 3 and go NO FURTHER. I have been running SP3 March 2008 Release for a month and a half and have had absolutely no issues. In fact, it runs faster and cleaner than XP SP2.

Thanks guys, these all sound like great ideas so i'm going to put them in place this evening and see what results i get. I never thought the colour blue could be so disturbing!!!

Hey Caperjack this was very useful except, i got as far as the chkdsk and it told me there were errors but then it didn't do anything else. Am i supposed to tell the computer to fix the errors and if so, HOW??? Its so confusing!!! I'm getting desperate to sort it out, any help would be fantastic!!!

If I remember correctly before you start CHKDISK you are prompted to "Automaticly repair errors" Try clicking that.
If not try a windows repair.

To Repair Windows XP from your XP CD…..

1. Re-start PC with XP CD in drive (Have your serial number handy)
2. As your PC starts press “F12” for boot menu (Or what your PC may ask for)
3. Scroll to and select “boot from CD.”
4. At prompt “Press any key to boot from CD” Press “Any key”
5. In the Windows XP Setup window, Press “Enter” to set up windows XP, (Don’t worry, this is a repair only, not a fresh install.)
6. At next window, Press “F8” to accept license agreement
7. Wait until windows displays your current version of XP and asks “To repair the selected windows XP installation press R”
8. Press “R”
9. Enter serial number when prompted.
10. Wait for files to be copied (PC will indicate 39 mins, it will take a lot less.)
11. When asked to adjust Regional language options, click “Next” as it is still set.
12. PC will re-boot.
13. If you have AVG Free, copy serial number to a file as you will lose it on repair. After repair a window will pop up asking how you want to treat AVG, Click repair and when prompted enter serial number.
14. Check to see if problem still exists.

I don't under stand this comment ,iam helping and if you are really desperate im sure there ar computer repair shops in you town/city

the "f " in the command stands for fix, in the list after it ran chkdsk it should have shown that it fixed x number of errors !

-Sorry caperjack i meant any MORE help would be fantastic, i totally understand that your doing me a big favour. Sorry if i sounded ungrateful.
I tried /f and that didn't seem to work, but my computer prompted me to do a /p which i did and this didnt do anything. I shall try the /f again.

-Bob, thanks for the 'idiots step by step guide' i REALLY need that, i'm so lost with computers!!! I got the cd off a friend as i have lost mine but theres no serial number, i shall ask my friend to provide, i'm sure they'll have it. Thanks guys and hopefully my next post will be a positive one