I was sitting on the toilet one day, did my business, got up and turned to flush and saw ants all over the wall behind. They were mostly tiny dark red ones with a few bigguns with wings.
I gather that they were fire ants...
It turns out that they had (somehow) got into the hollow porcelain tank lid and had nested there.
I ended up putting the lid in the shower, pretty much filling it with ant killer and then using the shower head to wash them out.
Haven't had a problem since.
Course, I would suggest that you disconnect the battery and CMOS battery before trying this with your laptop.
Once you finish, a good healthy spray of WD-40 should stop it getting rusty.
Your laptop may not work after this, but I guarantee it will be free of ants.
If it does still work... you may be eligible for Canonisation since this will be a verifiable miracle !