for ur CPU id say around 38 idle is normal temp.. and 50ish while playing games is fine.. my CPU (2.4ghz HT) goes up to 54 while encoding movies... on idle it goes as low as 31 ...
not good.. cuz its more dangerous if a CPU goes jumps 20C degrees between idle and load.. better to have it at say.. 45 idle n load at 50 sometin
try cleaning ur HSF maybe its dusty.. might consider changing the thermal interface material (the crap between ur CPU and heatsink) incase its gone bad