Computer Very Slow.

I shut my computer off the other day becuase it was 38 deegree outside and it was runnning at 56 degrees and when i turned it back it has turned very sluggish.Windows takes about 10-15mins to load.
At firsat i thought my CPU or RAM so i did a benchmark and they were fine but when i did my hard drive using Sandra File System Benchmark i got 3403kb\s and my second drive got 17mb\s so i was thinking it was the drive and was wanting to know if anyone agreed

Im on a Athlon 2600
512 PC3200 400mhz
Maxtor Diamond 40gb 7200(Main)
20gb Quantum Fireball 7200(second)

so am i right in thinking its my drive and get a new one or could it be something else


Cheers