Extremely slow boot windows 7 usually 8 -10 hours of waiting. To get to this point . has taken this computer 73 hours - from reboot because of hang up to restart. Then internet. Find page. Open. So far no one has answers or believes me, but to try sell me programs that don't work. I've run hunderds of anti virus, malware and other scans to no avail. Deleted history, defrag and unloaded and reloaded Windows 7. I'm this close to get a 3.1 computer which is light years faster with less hang ups.
There's definitely a problem with your hard drive. Replace it with any other hard drive to see if there's still trouble with extremely slow load times. If that hard drive is still low then I'd try maybe making sure the cords are all right. If there's still trouble then it's a mobo problem.
Meurglys made a good point about the hard drive. My mom had this exact same problem for months. IE, music, and everythang would take 10, 15 minutes to start up She tried so many thangs, and even tried to reinstall windows which didn't help, then I stepped in.
Quick solution, I replaced the hard drive and everythang ran smooth.
It sounds like the rotation on your hard drive has slowed down considerably.