I have no idea what could be troubling it. When I download I, the only thing that goes kind of slow is loading up web pages, that's common I assume.
The top 3 things I would do to fix this problem is:
1. clear some space on the hard drive, I'd make sure I have atleast 1/6 of hard drive space open, why I dunno.
2. Run Disk Defragmenter and see if that helps.
3. Run Virus, Adware, Malware any kind of ware and see if anything comes up.
And if these things fail, then I'd probably resort to a full system restore if the whole thing if it bothered me a lot.
I'm sure you did 1-3 PJ, but I still hope this helps anyone.
Also it's probably not the best things to do, but these are the things that I would do. I'm not computer savvy at all though. I would love to hear what the actual problem and solution is though.
