Yeh, i do agree it gets freezing down under (with no snow..). That is why i use my pc as a room heater

. Just wait till summer...
Although I still wouldnt cross out a temp problem so soon.
To expand on Tedster's comment on errors:
do you get sudden restarts or BSODs? If so goto
%systemroot%\minidump folder (where systemroot is your local windows folder), zip up a few minidumps and post here.
Do the spyware scan as Peddant suggested as well, to eliminate that factor.
Download Everest Home and/or Speedfan, go to the sensors page and take a reading while nothing much is running on your pc, then fire up a high intensity program like a game or something then take another reading. Post all the Temperatures, and also the voltages noted.
Also, do you remember any environmental changes (hard/software) recently/before/after this problem happened?