If I am not careful, this will sound just like an advertisement....
I don't care - when I find something as useful as this, and so beautifully laid out that a complete numpty can use it, I just have to tell the world.
Bottom line - I was brought a very sick PC that turned out to have so many viruses and worms that it would (barely) boot up to the Windows XP HE desktop, and no more.
I was sure that the fact it only has 256MB of RAM was contributing to the problem.
But... it was a Dell Dimension 2400 - and apparently they are very choosy as to what RAM they will accept - not just any old DDR1
The I heard about this CRUCIAL website, which allows you to find the right RAM in moments.
I am not allowed to place a link to that website here, but use your loaf, and you should find it!
You just have to admire the layout and ease of use of this great website. I have been trying to write user-friendly websites for over ten years, and this is better than anything I have seen (or done)
then you can buy from Ebay here http://stores.ebay.co.uk/Cilcain24
another useful freeware utility to download is CPU-Z (from CPUID Software Development Kit) which clearly identifies all the esoteric details of your CPU, Cache, Mobo and existing memory.