which fan to buy? computer locking up

I'm running a P4 3.0E w/hyperthreading and it seems that the computer started locking up on me yesterday every time I turned the computer on. I then reset all settings in Bios, no change. I tried a different hard drive, no change. The computer passes post, so I went into bios and the temps were about 69 Celsius. Then I took the heatsink/fan off and there was a lot of dust on there, so I blew that all out put back together, and still locking up.

I'm going now to get some arctic silver, but I'm thinking my processor may be fried. Been running fine for the past year but this all of a sudden started. I want to buy a not too expensive heatsink/fan off newegg.com but don't know which one. Any info is greatly appreciated. Thank you.

 

Bought some arctic silver, pulled the ram, and replaced ram one stick at a time bad ram issue solved

 

Here's the Bang for your buck, Just about the only thing better or cooler will be water:
http://www.jab-tech.com/Thermalright-XP-90-OEM-pr-2921.html
Add a Panaflo H1B 92mm fan. (Jab-Tech is great place to shop)
I didnt seen one at newegg, when I did they were more Money, another option at newegg would be the Thermalright XP-120 but it's a big HS, wont fit on some MOBO's
Newegg has a XP-90c but it's too heavy for most MOBO's

69c that will make her Lockup
Careful not too much Artic Silver, I prefer Artic Ceramic, clean's easier, & non conductive, a bit safer.

 

I have the XP-120 with a 12cm fan plonked on top, and it is fantastic at it's job, but ASUS is right, you need to check wether it'll fit on your board - I had to bend a couple of capacitors out of the way to get it on mine (Asus K8V deluxe), but it dropped the CPU temps over 20 degrees more than stock.
You may also need a special adapter to get the heatsink to sit on your P4board, but these are only a few quid, or 'bucks' .
You can check for compatibility on Thermalright's website:
www.thermalright.com