Windows 7 booting and freezing problems

Ok folks got some issue here with my PC. It seems that from time to time I get a freeze on the PC when I try to boot. When the PC can boot, and Windows loads, I get temporary and verry frequent "not responding" or a busy icon instead of the normal cursor, for no real reason. For example if I try to click a link on a page, it stops responding for a few seconds and than it is back to normal, it does it very frequent and because of that it's verry hard to work on it. I got 4 GB of RAM from which 3 are used since I have a 32 bit OS(through I don't think the memory is the problem), also say if I try to enter an URL in the web browser and I press enter it does the not responding thing again. If you're saying it's the browsers fault and I should reinstall it, it is not from the browser, since it does this on the entire PC, sometimes it even asks me to end the process of Windows because even Windows doesn't respond in some cases through it is not that often. From what I've found out it seems that there are some periods which the system can't detect storage drives(like DVD-RW,external drives and even HDDs). I'ved found the not seeing storage drives thing while trying to change the first boot device to the dvd-rw instead of hard drive to boot from the windows disc, but when I clicked the boot order in BIOS I was shocked when I saw only the floppy was available, the thing is I don't have any floppy drives on my pc. I also don't think it's a driver issue or corrupt windows since the installation is recent, and the drivers of the motherboard and other components are installed.

I had just opened the case of the PC and cleaned it of dust. Seems to go way faster now. Can dust actually cause problems like these?