Computer takes 8-10 minutes to boot, strange whirring sounds coming from hard drive

Hi, so I have an HP Pavillion Elite HPE that I bought about two years ago new. For the past few months, what I assume is the hard drive has been making a strange, loud whirring noise at odd intervals (not necessarily when I'm opening programs or doing something I assume is processer intensive). I've attached a recording of it so you can get an idea, it sounds like different cycles are phasing and the tone oscillates up and down until it peters out. i've noticed my computer seems noticeably slower these days, with explorer often crashing. the most disconcerting part is that whenever i restart it actually takes about 8-10 minutes to boot back up. It gets past the Windows splash screen and just goes blank there for a long time, then shows the desktop wallpaper and hangs there for forever too. Any ideas?

here's a link to the sound: http://www56.zippyshare.com/v/75350378/file.html

Oh, and I tried running TSG SysInfo and it says it's not a valid Win32 application??

Thanks!!