Hello! My Dell Latitude d800 started to lag horribly yesterday morning. I know space and memory aren't the issue. The fan has been running non stop, until the computer is cool to the touch, and is louder than usual. And every time I open an application (Chome, CCleaner, etc) it starts to lag and the CPU usage jumps to 100%. I thought something was wrong with the fan or the system its self, but when I log into the different accounts on the laptop, mine is the worst. The others still lag, but the CPU drops from time to time, and I can access the Internet without it hanging up. Also, I checked the processes in the task manager, and everything looks fine. I'm scanning my system for viruses again, but I was wondering if anyone could help.
If it is suddenly much slower, it is most likely malware. I would download and run Spybot Search and Destroy as well as Malwarebytes. They are both free and are very effective at finding malware. I think they do a better job than some of the big antiviruses like Mcafee and Symantec.