Quote Originally Posted by GBB
I have overclocked my Nvidia Geforce 6600GT to run at 1.5 Gb ( OMFG) and it has been like that for the past year. In short, yes overclocking works, and as long as you dont go uber crazy, its fine.

Some guy i know overclocked his card (same as mine) to 2.5 GB and totally burned his computer and set fire to half his house

Very Clever
GB = Gigabyte = memory
GHz = GigaHertz = clock speed

Now even if you meant GigaHertz, a 6600GT is clocked at 500MHz = 0.5GHz usually. If you had overclocked it to 1.5GHz, it would be toast now.
You may be talking about overclocking the memory, because that alsohas a clock speed, but I don't think that overclocking the graphics memory will give any big speed increases.

We had a topic about that before and I think the general consensus was that overclocking graphicscards is not as fruitful as overclocking CPUs and usually not worth the dangers.