M15X Sponteneously Not Responding & Lock up

So, I recieved this computer mid 2010. It is, decently old by end of the line standards, but all drivers are kept up to date. I've had no problems with my system of such until recently. My motherboard went out (Power issue) so it was shipped in to Dell to get a replacement. Since I've gotten my computer back, I have been having intermittent freezing, programs and tasks not responding, and the only way to resolve the issue is to inevitably hold down the power button and hope it doesnt happen again. I've always played CPU intensive games, yet whether they were running or not seems to make no difference, and the problem doesnt seem to be linked to any particular program/task/etc. If there are any others with the same problem that have resolved this issue it would be much appreciated! I'm almost considering rebuilding an entire new rig due to the intensity of the problem as of lately :/

I will do my best to provide any additional information you may need.
Thanks in advance.

 

I used to have the same problem.
I resolved it by removing Lojack. And I had another issue of stuttering and lags which came around a year later and that was due to McAfee.

 

I do not use either. I never installed lojack oddly enough, but i do use avast. Perhaps that could be the cause?

 

Lojack is installed by default.