Two days ago I went to clean out my system of dust, because I had over heating problems. I didn't have any canned air, and I was far to poor/lazy to go pick up a can from Walmart. So I went through took out my components and blew out all the dust (there was a lot of it). Everything was going great then I went to clean my CPU fan/heatsink. I couldn't get down and blow it out because of the amount of dust in the heatsink so I took it off. Here lies my problem the CPU stuck to my heatsink. To get it off I had to soak it in isopropyl alcohol (91%) to break up the thermal paste. After that was said and done I put my processor back in, and put more thermal paste on. I re-applied my heatsink.
Start up went just fine until yesterday. Now when ever I start the computer you will see and hear it run for five minutes before my boot screen shows up. After that my PC works just fine (as I'm on it right now.).
Wow you soaked the cpu as in under liquid?? Yikes you can 99% of the time get a cpu to come loose from a heat sink by twisting it from oposing corners. If not that just pry it off with something very carefully.. Anyway it's done now. I would try a full power down of the mobo unplug all the power connections and wait 5 min or so plug it all back up see what happens.
If you have multiple drives (including CD/DVD) you may have mixed up your SATA connections when plugging everything back in, check your boot order make sure your drive containing the OS is first, otherwise it will check every disc before hand for an OS including your USB drives, and DVD drives. If you did mix them up flash your bios, as well just to be safe.
If that doesn't work:
If your using a motherboard that you purchased standalone make sure that you plugged in all those little tiny connectors that run to the on/off button on your case, check your connections to your PSU, make sure everything's plugged in correctly and check all the connections with a voltmeter if possible.
Worst case scenario is you cause static damage when you were handling your motherboard or CPU, although it's not likely since it runs fine after everything boots
I've had very slow boot times before and the problem was usually a hardware conflict. Try unplugging one thing at a time, starting with usb devices and then go inside and disconnect your optical drive and any auxiliary hard drives. If you have on-board graphics and it came to it, I'd even remove my video card for a test. Your motherboard is testing all the hardware before it boots and something is not right.