HTPC with win 7 display issue

[j.o.s.h.1408]

Hardware:

The specs of the HTC machine are as follows:

• ABIT ice-7 pro Socket 478 Mobo
• 2gb DDR Ram
• Nvidia 7800GTX AGP Card(i had a ATI 9800gtx before)
• Intel Pentium 4 3.2ghz northwood
• Seasonic 450w PSU
• Chieftect full tower Matrix case

My issue is that i am running windows 7 ultimate and since running it, my HDTV would go blank as if the vga cable is loose. it never use to do that when i had XP installed on it. Is this a win 7 issue with low end hardware with its display drivers because on my work pc running a more up to date dual core cpu but with an onboard graphics card, the monitor goes blank when i have a lot of visual animated stuff opened such has movies or a few flash animated websites.

cheers in advance.

[CyberChris]

Are you running 2 displays at the same time as I have seen Windows 7 reverting to the other display (which was a TV) instead of the monitor.