Windows Vista black screen with movable cursor after welcome screen.

I've tried to solve it using recovery disk, unplug any connected cables, RAM, CMOS … cheked every thing but there is no change. Please i don't want to format my hard drive b/c i have important files on it.

Please help me figure out how to fix this! Thanks!

the current OS on this computer is me and I have absolutely nothing on this computer that i need to back up and save.
what is the least complicated and inexpensive way to do a clean install of xp onto this computer?
I would like to run this computer on a network with my other computer that currently uses xp.
from what the xp disk says, I can't boot to the cd because it has a license restriction to the original computer. I had to order the recovery disks cause initially it was installed into the hard drive only.

I use an Compaq Presario SR1103WM when I'm at my Dad's house. We've had it for about 2 or 3 years, and used it for everything from games to internet to whatever you can think of. However, it's outdated now, but I can't afford any major upgrades or to buy a new computer right now, so I'm trying to figure out how to run it better. The only specs I know are:

248 RAM (8mb is diverted to video memory) max is 1 GB
Intel Celeron(P) 325 2.56 GHz
40 GB HD

I have no clue about what the video card is, I've had it 3 years and still can't figure it out. Sorry the specs aren't very informative, but you could probably Google the rest if you need it. Right now it's on a dial-up connection, which I only use for instant messaging. Like I said, as of right now I can't really afford to upgrade it, but here in about a month I can. We're also getting Road Runner for it, which should speed up the internet connection a bit. Besides upgrading it, what else could I do to make it faster?
Also, I have deleted a lot of old software that I don't ever use anymore, and I just figured out how to clean the hard drive, so I did that for the first time in 3 years and it is sped up slightly.