Slow moving system, hung up often, loud/squeaky fan, BS-OD lately. no problems til new Internet Service dsl wireless ext adapt,(but new Norton 2010 luv it!)XP Pro. old comp, but babied & very clean.
Do you still have the BSOD?
IF you dont then download CCleaner and use the file cleaner and registry cleaner.
After that in Tools in CC use startup manager.
Basically anything that doesnt have to start remove. Keep only required programs.
You can google the startup programs to see if they are needed.
Also by the way Nortons 2010 is good but a real resource hog. Not good for older computers.
I recommend uninstalling it and running Microsoft Security Essentials which is pretty lightweight and free.
What are the specs on your machine?
Processor speed.memory size are most important.
As far as the fan.
Open case and blow out fans (and heatsink) with a can of compressed air.
Then tighten screws on fans if possible.
If still have problem then replace fan. Ebay your model. Fan replacement is pretty easy for the most part. Four screws and a power clip.