Loading attempts fail, wont shut down.

Hello,

my computer has been acting up, ever sense i got it sent back to me, "crashed after bombed by viruses, so i sent it in" and now, my pc doesnt always like to shut down. ill hit restart or shut down, and wait an hour, nothing happens "sometimes, like 50/50" also after time goes on, ill be on my pc, about 1-2 hrs later my pc will DC from internet even though it still says im connected. and nothing will load. i can click all i want on shortcuts and anything you can think of BUT nothing loads. it says it is loading "the mouse gets a little sand vial" but then nothing. i also cant load task manager, ill do CTRL ALT DEL, and click task manager BUT again, nothing shows up. my only option is to attempt to shut my pc down "usually doesnt work" so most of the time im forced to shut off my power.

any ideas? sorry the topics a but large :/