While your temps aren't too high right now, they have the potential for problems. I would install either rear exhaust fan, or a front intake fan to help cool your system down. The CoolerMaster HSF you have now should be fine for cooling your processor, but it is a good idea to have at least one case fan in any and all Athlon systems.
If it were me, I would be worrying right now. I never let my CPU get that hot and the one I did, I accidentally fried. I would do my utmost to keep my CPU temp and system temp as low as possible without shelling out tons of cash.
Not "melting" too hot, but I would be more comfortable if it were cooler, if it were my rig. However, if it dont lock up, it isnt broken!
"The Cash Left In My Pocket,The BEST Benchmark"
i set a 1.2gig 266 up in a minitower and it idled about 120F with an Alpha cooler on it and rear exhaust fan...the GF Quadro2 Pro in the agp slot didnt help though... nor the 7200 rpm drive... that sucker gets HOT!