I’m back to this PC freezing at windows again

Hi folks! what exactly runs the keyboard and mouse? I took this friends hard drive to work, it’s an IDE, and plugged it into my machine. It had 8 Trojans/viruses, etc. but they were all wiped off. why would the hard drive work there but not in the original PC case? the PC I’m writing this on is ATA hard drive, and I can’t seem to get it to work on this PC.