Computer running extremely slow

[sunet.dk]

Hi

I have a computer with dual boot winXP and FC6 that I stopped using for around half a year ago, but then a couple a month ago my girlfriend started using it - and despite it is a 5 years old Dell Inspiron it was runnning alright. But the suddenly the computer started to run extremely slow already from when it is booting - it takes 3-4 hours to boot up. Even when trying to edit the BIOS setup, this is very slow. The computer had been turned of a couple of weeks whe it happend, but before it had been turned of for a couple of month.

So fare I have tried the following things:
I managed to boot it up in windows, and in the system tools it still said 1.2 Ghz, 512 mb ram and the date and clock was correct despite a couple of hours.
I have now tried to remove the harddisk and mount it on another computer, and it seems to be running fine.
I have tried to boot from a linux livecd, and this maybe seems like it runs the first couple of seconds fine, and then it stops.
Then I tried to boot from an old bootdisk, which also boots up a bootloader, where I can select the system I want to boot, but when I select one, it stops (this might also be because it is an old bootdisk, which does not match the current fc6).

Can anyone help me identify what the problem is?

/Sune

[lmo]

If the cpu fan broke down or the cpu/heatsink connection failed, the cpu would overheat = slow.
If any cooling fan stops, it is dangerous. Too much dust can block airflow and cooling.
Dropping it (even gently) could easily knock something loose (ram fell out).
Installed a virus? (Not likely to affect linux or bios)
It could be anything, and fixing it might not be free.

[sunet.dk]

On your inspiration Imo, I opened the laptop and blowed some gentle air to remove dust - and I could see that there is only one fan for the cpu, which I know this was running fine, so I closed it all again, inserted the harddrive again - and then it was running all fine as before... Strange but nice :-)

Thanks for tip.