DirectX from the "directX website"? If what you mean is microsoft.com then you are lying as it is impossible to install DX10 on your OS. If it is from anywhere else, such as Alky Project then it is probably causing some sort of problem.
What you fail to realise is that your card does not support DX10 at all. Even if you had vista, is has not got the capability of displaying DX10 as it is too old and was around before DX10's invention. I have heard mixed things from DX10 XP, but all of those mixed results come from people running DX10 capable hardware, and the mere fact that you are not seems a pointless recipe for disaster in my book, especially as you will see no gains whatsoever with your card.
As for linux, you just download and burn to a disk, then pop it into your drive, make sure your drive is first boot, and select install if there is no "LiveCD" option. This will bring you to a desktop similar to that of a Windows PC. If you have artefacts on that desktop, it is a hardware problem, else it is drivers etc.
Linux can be downloaded in different versions, but seeing as you will only be using it to test, I suggest you get "damn small linux" to save download and burning time.
Find it here
http://linux.com/directory/Distributions/LiveCD/Damn-Small-Linux/details