Help with overheating computer

OK. Let's see if I can explain this in a clear and concise way.

Specs:
Processor: AMD Athlon 64 x2 5000+
Motherboard: Foxconn AM2 NVIDIA GeForce 6100 + nForce 405 Micro ATX AMD
Harddrive: SAMSUNG 200GB 7200 RPM 8MB Cache
Memory: Two 1gb memory sticks

And a graphics card which I forgot the specs on and am too lazy to look up right now.

My problems are as follows:
º My CPU (stock heatsink) gets too hot according to SpeedFan (as far as I know). Currently my temperatures look like this:
http://www.allanne.com/speedfan.png
º Also, sometimes my harddrive clicks, and I lost some data off my D partition (just files). I'm assuming it was related to that, at least. My C partition is programs. This only happens occasionally, that it clicks, and so far it's only deleted stuff on my D.
º One time my baby sis unplugged my computer, and since then it wants to run the scan in the boot sequence, but it never runs, it says 0 percent completed until I restart and bypass that.

My questions are:
What do all the Temp1,2,3, Core, etc mean?
Should I buy a new harddrive?
Should I buy a new heatsink?
How do I make it scan when it doesn't want to, or fix it?
Does anyone have any other advice?

Anne needs help... :-/