While installing an Asus M4A88TD-M/USB3 motherboard I managed to pull off the Northbridge heatsink. I put it back on but I don't know how well it's on. What do I need to do to be sure it's okay and if it isn't how can I fix it?
I have heard about some northbridge heatsinks being loose in the first place. Now if it was so loose that you managed to pull it off, I would fit it back on and see if you can pull it off again with reasonable effort. If you can't, then power it on and watch the temperatures in the BIOS.
If you want to be completely risk free, send the motherboard back saying that this heatsink is loose. If it is still under store warranty, great!