8800GT - No Signal

Right so I've had my PC for about a year now and ever since the first day I've been having issues with what I think is related to my graphics card or my motherboard.

So.. Whenever I try to play older games e.g. Guild Wars my monitor will 'Switch itself off' so it seems and give me a message that says 'No Signal'

I've tried various ways of fixing this issue with no luck..

I did find one way to stop this from happening so quickly which was underclocking my graphics card.

I would like to be able to use my graphics card to its full potential so I'm asking if anybody has had this problem and has been able to fix this issue?

My system specs are:

CM eXtreme Power 460W PSU
Seagate ST3250310AS 250GB Hard Drive SATAII 7200rpm 8MB Cache
Optiarc AD-7191S 20X DVD±RW/DL/RAM LightScribe Serial ATA
Intel Core 2 Duo E8400 3GHz (1333MHz) Socket 775 6MB L2 Cache
Gigabyte GA-P31-DS3L iP31 Socket 775 8 channel audio ATX
Creative SoundBlaster X-Fi Xtreme Audio PCI-Express
3GB RAM Kingston 1.8V
Point Of View 8800GT 512MB GDDR3 256bit Dual DVI PCI-E

I don't know what details you'll all need so ask if you need anymore.

Any help would be greatly appreciated, so thanks in advance all.

Thanks for the reply.

Well I've tried all sorts to fix this after being told that my PSU was capable of running this card but I'm open to all opinions as I don't really know where to start with power issues.

Basically.. Underclocking only allows me to play games longer.

This is something I forgot to mention - Newer games such as Crysis (High, no AA) and CoD4 maxed out run perfectly for hours and hours on end.

Other things I've tried to do to sort this problem are:

Flashing my motherboard BIOS,
Flashing my graphics card BIOS,
Reseating the graphics card,
Adding more cooling,
Tried all sorts of drivers,
Removing other pieces of hardware such as my sound card as I was told that could cause problems,
Removing some of my RAM,

I have also tried to fiddle with my monitors EDIDs but I think I'm getting a bit in too deep here as I know nothing about it.

What other information might you need?

I've also tried this plenty of times and it didn't help for me.

Thanks for the suggestion though

No it's not.
I'm confused as to why it may be the PSU if it still continues to crash even when I underclock - It just takes longer.

I suppose I could try something to test if it is my PSU and let you know how it goes.
Thanks

Don't listen or buy anything yet. Start logging your card's temperature and fan speed and the psu voltages. Make sure the temperature is staying below 80C or so and that the fan is working correctly. Monitor the voltage to make sure there are no large drops and that it is close to the nominal 12V voltage. Then you will know if it is a power or heat problem. Unless the psu is failing 460W is much more than you need. If anything it sounds like a cold solder joint is breaking once it has been heated. There is a thread you might want to google or digg regarding "baking" cards (that's right cooking it) for this type of problem. Definitely not for the faint hearted.