The Internet can be a dangerous place. Most of what you find there is useful and interesting, but lurking there are many threats. They do their best to look innocent. Always think three times before allowing a download that will alter your computer. Carefully read the little boxes that come up and READ BEFORE you click OK.
A lot of web sites will offer to make your computer run better. 99% of them are either security threats or will do the opposite – slow it down. Avoid “toolbars” like the plague. They are worthless and will slow your computer.
You need security protection software running and up to date. There are really only two components to security: antivirus software and a firewall.
The firewall that is built into your operating system is the best. Do not install any other. Antivirus sellers will try very hard to sell you their “Internet Security” programs. Do not buy them! You want only antivirus software.
Good antivirus software is not only effective but does not slow your computer. Antivirus software should be updated automatically very frequently – like several times per day. You will need to pay annually for the subscription service to keep it up to date.