My Computer Seems Sluggish
Symptoms
Your computer loads web pages very slowly. Programs take forever to load and run. Your hard drive constantly cycles. The computer takes forever to boot up and seems to freeze up often. Does this sound like you?
The Likely Culprits
Spyware: This is definitely the most common cause. Spyware can come from banner ads, ActiveX Controls, file-sharing programs, shareware, or a variety of other malicious downloads or websites. Spyware eats resources and bandwidth to send you ads and other content that you may or may not want, so you will see slowdown in computer performance, an increase in boot time, and hard drive cycling, probably accompanied by a laggy connection and constant pop-ups. To remove spyware, check out the Dealing With Spyware Guide.
Fragmented Files: The second cause of sluggishness can be a fragmented hard drive. The computer spends too much time searching for pieces of files all over the hard drive, and this slows down disk access and load times, including boot-up. The solution is to defragment your hard drive--check out the Defrag guide.
Viruses: Viruses can definitely interrupt computer performance, and are the most serious of the problems you will encounter. Check out the Removing Viruses guide for help.
Low Disk Space: This can squeeze virtual memory and degrade performance. There are a few ways to fix this: delete files and programs you no longer use (see the Optimizing Your Computer guide), compress your hard drive, ZIP up files not commonly used, or get a larger, or second hard drive. You can also copy rarely used files to CD or DVD and then delete them from your hard drive, like music or movies, and run them off the CD if you have a fast enough drive (see the Backing Up Data guide).
Invalid Virtual Memory Settings: A bad virtual memory configuration can increase page faults, slow down your computer (because there isn't enough or too much memory to address), and make the hard drive cycle often. Virtual memory settings are usually under Start->Settings->Control Panel->System->Performance. The best setting is to allow Windows to manage it, but if you suspect this is the source of the problems, the best manual settings are: the minimum size 1/2 your total RAM, and maximum size two to four times your RAM, depending on your applications. Tweak them to get best performance.
Old Computer: Sometimes your computer just can't hack it. If you have an old computer, upgrade it or buy a new one. Adding RAM is the cheapest and easiest way to upgrade, and gives the most noticeable performance. You can also get another hard drive, a faster processor or better video card. If upgrading is not an option, ensure the applications you are trying to run aren't above your system's statistics--in short, the minimum system requirements for all applications should be decently below your computer's abilities. You should have a good amount of hard drive space left, few items starting up with your computer and you should try to only run two or three programs at a time. Also, ensure you are running an operating system that is on par with your system--in short, don't try to run Windows XP on a Pentium I.