Yup, that's perfectly fine temp-wise. Mine usually runs around 50C or lower; since temps here have been running 80-90 during the day that 50C is normal.
Typically you should see between 40-45C at idle, and under load anything under 50-53C is okay. If you get up around 55C you're starting to BBQ stuff. Check and see if your temp checker has an alarm built-in. PCAlert 3 (from MSI) has one, and damn is it effective! Sounds like a whooping siren blaring through the speakers when the temp alarm goes off. Definitely a good thing!
Redline for Athlon XP's is 55C, while a T-bird or Duron doesn't redline till 60C. Up at my local ISP the chief geek was stunned when I told him his beloved P4 was getting cooked at 70C. Sure enough, about an hour later he calls and says "my processor got fried!". I couldn't help myself: "Original recipe or extra crispy?"
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Flakbait [Delta6]
Delta Six's Flight SchoolPut the P-61B in Aces High