It's hard to say what the problem may be with your computer since you provided very little information. Slow computers can be related to both hardware and software problems. Since you already ran Emsisoft to check for viruses/malware, you may want to check your System Startup (msconfig) for bloated software. You can also check your Event Log to see if your computer is reporting any error that may be related to the hard drive. It may come down to having to get professional help if it's a hardware problem. such as a failing hard drive or memory issue.