Surfing the internet can easily introduce Viruses/Malware/Adware to your computer system. Be sure to have a reliable anti-virus application installed on your system.
Some tell-tale signs of malware issues:
Slow computer response and slow startup time
Random ads pop up on your screen even when you're not surfing the internet
Home and Search pages change without your input
Software won't launch
If your system is bug-free but still sluggish, you might need a tune-up to clear up general issues and improve performance. Tune-ups are recommended every six months, depending on your usage and demands. If you ever have a question about an update that you're unsure of, please call immediately to verify if it's authentic!