text: my computer is running very slow from some day. i scan my computer by antivirus saftware but no effect.? my computer is pentium-4, 2.4gh speed, windows 98 start with the simple steps that can't screw up your pc first! while most of the answers here can be correct, do one step at a time. especially messing with your start up files (msconfig). i say make sure that you make sure performace is set to programs. system properties > advanced > performance options > and choose adjust for best performance. letting windows choose for you causes problems. next go to add/remove programs and remove out of the box extraneous applications that most manufacturers install such as aol or symantec anti-virus (if that's what you're not choosing to use). than start the steps of the other answers.