Vista complete slowdown

Hi, I have recently got my computer cleaned of malware and I was re-installing all my software/programs etc. Earlier today, there was a power failure in my house and I checked the fuse box and started the computer again. When it was starting up, the power failed again causing the computer to shutdown during startup. When the power turned on again, so did the computer and it started with 'Startup Repair'. It was about 2 hours into the process when the power failed AGAIN for the third and final time. When the computer restarted, startup repair didn't come up and the Windows started normally, only that, IT WAS REALLY SLOW. It took me half an hour to startup Google Chrome.
My power is stable again but I am worried as to why my PC is so slow. Is there any way I could get it back up to normal speed? There have been MANY previous occasions where my PC is randomly SUPER SLOW on startup and then there are times when it's really fast. Also there are times when my PC turns itself on randomly.

PC SPECS:

• Model: HP m9265.uk
• OS: Windows Home Premium 32-bit (SP2)
• Processor: Intel Core 2 Quad Q6600 @ 2.40GHz
• RAM: 3GB
• HDD: 750GB

Power cuts like that can kill systems, and from what you have described one has to wonder if it has done any physical damage to the system, using a UPS device is the recommended suggestion to protect from these things, my guess is at a minimum it has corrupted the system, and the surest solution to this is reinstall, it is a pain no question, others may suggest trying a repair install if you have the disk, either sent with the system, or with what they recommend all users to do on first boot and thats create your own disk, but many don't bother with that, you may have an option to repair install from within it's built in back up, the one that reinstates the system to out of the box state, look for options within that area for a repair option.

Not sure what way to send you, try reinstalling and see how that goes, or run some hardware scans to see if any components have been damaged, I would suggest doing the hardware scans regardless, the UBCD has many tools on it, and the main ones to run are the memory tester, and the hard drive, download and burn this file to disk, then boot to it, use the arrow keys to move around, hit Enter to go into the sub menu of a title, and IIRC hit the Esc key to back out to the previous menu, these may or may not find issues, but if you have an unreliable system after reinstalling you may find something is on the way out, not much help I'm afraid, but thats what I suggest based on your situation, hope it's an easy fix.