Overheating

I have a PC with LGA775 Socket CPU. The CPU was overheating and there was a lot of dust on the fan. I removed it and cleaned it but it had little effect. After a few minutes of use and CPU intensive work, the fan starts making a lot of noise.

It seems the thermal interface material is damaged. Do I need to get a new fan or can I get thermal material and apply?

Thanks,

Ya it seems to br thermal interface is damaged. You need to buy now , it will easily available at computer electronics shops. First make sure that your all your fan-clips are properly attached.

Is the fan or heatsink clogged up (dirt)?
Is the heatsink seated correctly?

Clean out the fan and the heatsink thoroughly, clean off and reapply some thermal film between the CPU and the heatsink then reinstall the heatsink and fan back.

BTW make sure nothing is wrong with the fan's efficiency spin wise.

As lorenz said it before, replace and put new paste but make sure you clean processor and heat-sink from old one!!! And do not think if you put more paste it will be better. Put just a little as suitable.

Also, did you clean heat-sink from the dust (I am assuming that you did as you had already cleaned fan, but just asking to be clear).

If the fan spinning is not good, you should have on mind to buy fan, it is not expensive and it could do a lot on chilling inside case.