Having a couple problems with my i7 build

Hey guys,

After a long hiatus, I'm back, and I am in need of some help. My build is starting to really have some problems, and I'd appreciate ANY help that could be provided. I'm laying out all the main problems I've been having over the last few months, and so I know it is kind of lengthy, but I know how helpful everyone here is, and so I was hoping for a bit of advice from those who helped me put the build together in the first place.

I recently put together an i7 920. It has an EVGA X58 mobo, gtx 295, 6gigs of ram, and a western digital black caviar 1tb hard drive. Over the last month or so, it has gotten progressively slower and slower.

A while back it got so slow I reinstalled Windows, and some of the lag went away. But a lot of the things that the computer used to excel at, such as running many programs at once, and not lagging in the bit, as well as being able to initiate any program immediately, and booting up extremely fast, have been doing a lot worse lately.

When I boot up the computer, it takes about a minute to boot up completely, and that include about 10 seconds waiting for the system info window to pop up after logging in. Also, it is having trouble running more than 3 programs without any lag. Now, it is even lagging when there isn't much open at all. I'll be moving the cursor along, and click on something, and it'll take it 2-4 seconds to register that it has been click, such as an icon or a pulldown menu, or something. Also, whereas it used to take about 1 second to open a program, and maybe no time at all to open wmp to play an mp3, it now takes 3 seconds or more for either one.

Also, in games, I'm noticing a lot more refreshing lines appear when even only a few things are going on. It used to be that I didn't see almost any lines goes down the screen. It looked completely smooth.

And finally, just today the speakers have started acting weird. Well, really it isn't even the speakers, because the headphones are having the same trouble. Randomly, I'll hear the sound through only the right side, then only left side, then I'll hear a deafening loud noise, then it'll randomly switch around like that. Any ideas on this one?

Some side comments, that are nonetheless important: Recently, about 3-4 months ago, my computer fried its motherboard because of a thunderstorm, and it disabled one of my PCI-E slots. I sent in the motherboard to EVGA and got a replacement. Upon putting the computer back together, I found that the core temperature had skyrocketed from ~45C to 84C. I reassembled everything, making sure thermal paste was correctly applied, and I'm still getting the same temperature readout. I just ignored it. As dumb as this following statement might be, do you think this may be the root of my problems? And if so, how do you think I could fix it (maybe it is just a sensor problem? That's what I'm assuming).

Like I said; any advice would be GREATLY appreciated.

-Andrew