freitasm: It's so many things that blaming "Windows" is hardly correct. Anvitivirus software for example (as noted there are inline scanners, including Avast, ESET and others). Then there's drivers (updated to latest video, latest Intel RST, Intel Inf, etc?) and so on... If you are using SSD have you disabled Superfetch, Defragmentation, enabled TRIM (Windows would do it by default but not if you copied an image from another drive)?windows 8 is fine just happened with the 8.1 update. The only antivirus is the built in one. Yes have SSD and had clean installed windows 7 home premium on it then updated to windows 8 pro. Updated the latest windows 8.1 drivers from hp site and also from intel to try and fix it.
I feel the windows defender is adequate enough for me so dont have any other antivirus installed