strange happening

I turned my computer off about 11PM as always . next morning about 6AM electric went off . computer was still turned off . about mid day the electric came back on . I tried to start computer . nothing happened .I tried about a dozen times still wont come on. I unplug it let it sit for a few hours. still wont come on. I walk away and a few hours later I tried to start it again . it came on but it's so slow I dont know what to do .or what happened to it . its been a few weeks and still slower than ever. IE does not want to load at all. I do all the usual defrag run anti spy and disc clean up. I run spy bot and adaware .nothing will speed it up again