Hi Jade Knight,
Sorry to hear you are still having problems.
On the lights went out issue - ever considered getting an uninterruptible power supply (UPS) to avoid the power failure hard crash? Hard crashes can cause file corruption, loss of data and other headaches.
On the brutally slow and freezes computer problem, with both Internet explorer browser and firefox browser, this can be caused by a number of issues:
1-badly defragged computer - regularly defragging will speed up your computer
2 -too many startup programs - take a look at what is starting up and always running in the background
3 -if you don't already use a tool like ATF Cleaner to clean out temp fileshttp://majorgeeks.com/ATF_Cleaner_d4949.html
Lots more issues can cause a slow computer see this for more help
Slow Computer/browser? Check Here First; It May Not Be Malwarehttp://www.bleepingcomputer.com/forums/t/87058/slow-computerbrowser-check-here-first;-it-may-not-be-malware/