Ok, thanks everyone, particularly CCT and CMH you've both been a great help.

DCMeigs- nice to meet you!!!!!!!!

I have the same issue with my Dell 4600C. Do the posts holding down the heatsink to the motherboard complete a circuit to tell the computer that the heat sink is there? If so, just thermally glueing the heatsink won't help, right? Don't we need to solder in a new hold down? Or get another motherboard?

Just go buy a new one from a used computer parts store only like 2-3 bucks.

The chipset 'arms' are, from what I read, part of a circuit to tell you the heatsink may be loose.

If it is indeed unattached and one arm is broken/unsoldered, you can try a repair as noted above OR buy a 'new' mobo and hope for the best.

This seems to be a common occurance with that mobo (never acknowledged by the seller btw - what's new!).

If they may be part of a circuit to tell you the heatsink is loose, there should be an option on the motherboard BIOS to disable this check.

Once that is done, glue away!

Personally, I'd prefer something to physically attach it to the motherboard, because if it slips, its going to short something on your graphics card, or short some pins on the motherboard itself. And given that glue might soften when heated, it just might slip, so unless you know your glue well, I'd have something to hold it in place.

use electronics cleaner. Alcohol can leave a residue and household alcohol is a solution with water. Definitely not recommended.

Well, I've always been using 99.7% isopropyl alcohol, and I've always made sure that it doesn't look wet before plugging it in. And I've never seen residue...

But then again, residue can be really tiny, so I won't say anything cos I don't know better.

All I know is that I have always been using isopropyl alcohol, and it seems to work. This includes chips, and even on the circuit board itself, when I accidentally got AS5 on it.

isopropyl is a poor cleaner. Plus it leaves a residue and the water doesn't help either.... electronics cleaner is cheap, evaporates very fast, and cleans thoroughly. I use it all the time to remove thermal grease from pulled CPUs.

Well, 99.7% means there's probably no water in it, the 0.3% is probably other impurities....

But I should give electronics cleaners a go....

But they're all hydrocarbons anyway, whats the difference?

maybe so- but electronics cleaner uses some pretty powerful solvents.....

water and alcohol are poor oil and grease solvents.....

it's just chemistry.

hmm... forgot that alcohol was a polar substance...

I'll give electronic cleaners a go...

I'm surprised no one mentioned this, do you have a separate gfx card install on the mobo? if so when your HS fell off it might of landed right on it, if it did chances are the video card got damage as some of them are thin as well as any other expansion cards that were beneath it. Make sure they are all okay unless you use onboard video, sound, lan etc.

Aside from the thermal paste do we need any other type of adhesive to keep the heatsink on or will the thermal paste provide enough support?

Some days your CPU just smells slightly less than fresh....

OK, Isopropyl can be used as an anti static agent when painting fiberglass if anybody cares. Actually, I don't consider it's solvency very high, with respect to grease and oil type deposits.

Arctic Silver markets a 2 solution kit for cleaning and prepping the CPU surface. I assume they know what they're doing, so I bought myself a kit . The second solution, (the one that preps the CPU surface), smells lemony fresh and nice. You'll never convince that's a bad thing, so just don't you even try Misters.

I Have Some Good News and Some Bad News.....

There actually is thermal adhesive, (epoxy based); http://www.newegg.com/Product/Product.aspx?Item=N82E16835100005 Sadly, it's not really intended for CPU heak sink fans. (They're probably way too heavy).

you could try glue gunning the cpu chip and applying your heatsink back on top =]

super glue...?

This same thing happened to my mom's HP Pavilion a810n desktop computer. She past away a year ago and now my dad uses it mostly for e-mail. It's on 24/7 so as not to need waking it or starting it up.

Long story short (I posted elsewhere here in a reply about the same PC with heatsink falling off), I found the missing "clip" which looks like a circuit jumper with metal hoop on top and put it back after adding 'super glue' to the bottom of it.

The thermal paste on the chip and heatsink seemed good enough (for all I know it might be bad) because I could slide it around and it was sticky.

I bent the wire spring straighter to make it less a strain on the clips yet still hold okay.

To get power back into the PC I had to disconnect and reconnect the PSU to the motherboard while plugged into the wall AC.
Moving the computer meant unplugging and so lost power again, had to redo the fix a second time.

I would guess the chip has a problem now but the computer works okay I think. There had been complaints of it being slow, so I wonder if it was getting worse long before now.

Anyway, glueing the clip was my quick fix rather than trying to remove the motherboard and soldering so I hope it will last awhile that way.

I think people should at least take a look inside their desktop computers even if nothing seems wrong. Could prevent an unnecessary PC or motherboard replacement.