Sound but no picture

I bought a new computer 3 weeks ago and I've been having problems with the live tv in windows 7 media center. When I first setup the computer WMC was working perfectly. I was able to watch tv and record tv without a problem. Then after about 5 days of it working, I turned my computer on and I started receiving messages that the recording couldn't start because no signal was detected. I opened WMC and when I clicked on a channel I would see a gray(or sometimes its red) screen, no picture, yet I still hear the sound fine.



After 3 days of it being broken and only showing the grey/red screen, it fixed itself and started working again. It worked for about 4 days and then it broke again. This time it started by the picture going all wavy, and the red/green colors were out of sync. It kept getting worse and then started showing the gray/red screen again and not being able to detect signal. Its been unable to "detect signal" for over 1 week now.



I've tried googling it but I can't find a solution. This is a brand new computer! Not sure why it worked one night, then was broken when I turned it on again in the morning. I've updated my TV tuner and graphics card and that didn't help. I'm not that computer savvy so please help me fix this.


Not sure what info you need about my computer. If you need anything else let me know.

- Dell XPS 8100, Windows 7 64bit, ATI HD5450 Radeon, Hauppauge 1250 tv tuner


Thanks,
Valerie

Should I download the WinTV version 7 application and driver, or the Windows Media Center driver installation package?

I have already done that one and it didn't do anything.

You mean open up the computer and check the cable connected to the tuner? Sorry for being so dumb but I've never done this type of thing before.

I had already tried to reconnect the cable attached to the tuner and run the setup again. When I run the setup it says it can't detect a tv signal, then gives me the option to let it try again or configure it manually. If I click manually then I can go through the process but the signal still doesn't work. I only get a gray gray screen with sound, no picture.