i just built a new custom desktop pc and i am using amd II x4 phenom 2.6ghz
with vista on 1gb ram with 160 and 500 gb disks on a standard midi tower case which supports 3 80mm fans (i think thats the problem)
the problem is that my asus m4n78 pro is working on 67-69 degrees and the gpu on 46-49 degrees and i am scared of braking it...!!
i have a cpu (amd),chassis(akasa),and power (akasa)fan connected...
If your system is stable (no artifacts, bluescreens, or freeze ups) then you should be ok. I am surprised your system runs well with just one gig of ram. I would use at least 2 gigs. But be sure the second stick is exactly the same brand and type. Mixing different ram is never good.