probably just poor general pc maintenance, free up your memory, see what background programs are running like rhythm say's, check for spyware, adware, virus', trojans, empty temp folders, do a defrag, uninstall any programs you dont use anymore etc etc. I've found since i started looking after my PC a bit more and tidying everything up inside it re files, folders, samples, getting rid of samples i really dont use or want etc that my machine runs alot more efficient. Nothing worse than a slow PC when trying to do tracks