HP slimline Review

I bought this computer a little over a year ago, shortly after  my sister bought one.  It has slowed down considerably. So has my sisters.  I didn't come with enough memory, so i bought 2Gb and it worked well at first.  I thought that maybe it had to many programs or maybe even a virus/malware, slowing it down, plus it kept getting blue screen errors and restarting itself.  So I reformatted the harddrive, and now it's even slower. The processor is almost constantly running at 100% before, it was at 40-50%. I can't hardly do anything on it now, I can't even imagine how slow it would be if I were to install the software I had on it before.  It looked like a really nice high-end model when i got it, the keyboard has useful buttons like eject for the dvd rom drive, and buttons to control playback of music and videos.  It also has slots for any type of memory card which is essential to move files from my camera or phone quickly on to my computer or vice versa. It has an expansion bay, with i don't use, I spent about $350 to $400 on it, so I guess you get what you pay for.