I use a HIS Radeon X800XL and a P5LD2 Asus mobo.

Alright, so I download this fan/temp monitor software called speedfan 4.28 and run it. I get these stats

Sys Fan: 0 Rpm
CPU0 Fan: 2550 Rpm
Aux0 Fan: 0 Rpm
CPU1 Fan: 0 Rpm
Aux1 Fan: 0Rpm

So I assume the sys is 0 because my case fans are antec tricool fans and use manual 3-speed switches and ain't really connected to the BIOS; that the CPU0 is my CPU fan and that everything is fine with it; Aux0 would be the mobo fan but I don't have one on my P5LD2 and that the remaining 2 would have been extra fans which I don't have.

I set my CPU0 to 1900 Rpm to balance the noise/temperature and that's pretty much all I do.

Then when I check my GPU I discover that it isn't spinning anymore. I tried uninstalling this monitor software and even uninstalling the videocard and re-installing it with new drivers but still, it won't spin. I also tried to run counter strike source for a 30 minutes to get it hot and make sure that it isn't just idling, but still, it won't spin. Then I try GTA San Andreas on the highest settings with high res and after 5 minutes my graphics get bugged and everything goes black like if the computer had been shut down, 5 seconds later it comes back and I can see the same bugged graphics again until it goes black again.

So what do you think, might this software have screwed up some drivers so I have to re-install windows or is the GPU just not hot enough for the fan to start or is the fan broken for some reason?

The fan is usually just glued on. There are fan replacements available. However, the wisest choice is to replace the graphics card. It will burn out quickly if you do not.

I read where someone had a iceQII arctic cooler on one of those cards - maybe look at fan replacement/upgrade.

you guys sound pretty sure that it is my fan that is broken, because it can't be disabled through software or BIOS, can it?

In that case I'll just head over and get an Arctic Cooling VGA Cooler ATI Silencer 5 for 20 Euro at my local store.

Can you disconnect the fan connector from the vid card and hook it to a mobo fan outlet?

When I start up my computer today the fan is spinning perfectly, just as it did yesterday but if I now reboot my computer it will stop to spin, or at least that's how it was yesterday. So to make it spin again I have to wait a night before rebooting, like 8 hours or so.

Now, this is kinda wierd, does anyone have any idea of what is causing this behaivour?

CPU fan, Power Suppy fan, or both?

Oh, I suppose it is the GPU fan? That fan is just bad. When cold before the bearings swell from the heat, it can work.
I suspect that if you leave it running a while, it will freeze up and stop running.
Be ready to shut down if the fan quits, but let us know if it quits on its own.
These fans are infamous for failing. They only cost 21 cents.

Never thought of anything like that, does it actually happen? If so maybe I should try to chill my computer down and try booting it.

Though, it moves just perfectly when you blow at it so it would be strange if the bearings were blocking it.

Although it's strange that it works fine 2 mornings in a row and now it stops again.

I'd replace that fan. Chances are that its going out. So if you'd like to prolong the life of your graphics card then just buy a new one.

Ladies and Gents - I read in a post today that someone had problems with GPU fans and ACPI - if you catch anything like that please make a note of it.

tx