PC on its way out?

I have an ACER PC with a Q6600 processor 2.4GHz and 3GB RAM running Vista Home Premium. Bought in 2007.

It takes a lot of effort to get it to start. Sometimes the ACER start screen stays forever. Reboot from powerbar.

Sometime the System Repair option is offered, which eventually suggests a System Restore, but then it locks up during the procedure. Reboot from powerbar.

Sometimes it works, but then it sighs, (I kid you not. It just loudly sighs) and shuts down with no procedure, just off.

I recently replaced the on board ethernet connector with a separate card due to a storm related issue that destroyed my modem, my router, my onboard ethernet connector and my big speaker. Could that spike have done something else that is only now showing symptoms, or is it just getting old?

Pretty much everything I need I've backed up, and I can afford a new one if I have to, but I'd like to know if it's repairable.

Thanks for any help on this.

 

I've never replaced the power supply. I use the free version of Advance System Care every week or two.

I clean out the box with a vacuum cleaner every now and then, as it gets quite dusty in there.