Which of my hard disks is failing - need help identifying

Hi guys, I was wondering if somebody could help me out. I gave my pc a much-needed dusting off yesterday and when I tried to turn it on again, it started acting up. At first windows was freezing every 10 minutes or so, then several times that I tried to restart it, it showed something like "disk error press any key to reboot". I thought some connections were just not properly inserted when I put the pc parts back together so I removed them again and made sure they were properly placed when I put it back. It worked, I used the computer for about 4 hours last night before going to bed.

Then this morning, it was back to freezing up every 10 minutes or so. I've read somewhere that this is a sign of a hard disk failure, could someone help me confirm if this is the case with what I'm dealing with right now? I'm not sure because maybe I just messed up the connections of my harddisk to the motherboard since the problem started after I cleaned my pc and put it back together.(I was totally careful about putting it all back but then again, I'm not the most knowledgeable guy in assembling back pc parts)

Also, if it is indeed a hard disk failure, I have two hard disks on my pc, one is a 40 gb drive c where only windows is installed and another is a 500gb drive d where all my files are located. Of course my first thought is that the drive c is the one broken, but is it also possible that my drive d is the one acting up?

Thanks for reading this and I really hope someone could help me sort this out.

-Kev