How to clean an infected PC and keep it clean.
PCs can get infected many ways, some accidentally, some by poor choice of web pages, some by carelessness and some by deceptive emails.
Regardless of how it got infected, you do want to clean it off as soon as possible.
There are two major types of infections: by virus and by malware.
Viruses can slow the PC; add, change and delete your files, effectively corrupting your information and data. Viruses are serious infections.
Malware, a general term for spyware, trojans, etc., infect your PC and can steal your information, your address book, send emails out under your name, use your PC as a relay, effectively slowing your pc to a crawl.
You must scan your PC for both types of infection and delete or quarantine the infected file(s).
There are lots of anti-virus (AV) programs for sale. Here are three AV programs that are FREE for personal use.
AVG - http://free.avg.com/us-en/download-avg-anti-virus-free
Avast - http://www.avast.com/free-antivirus-download
Avira Antivir Personal - http://www.avira.com/en/avira-free-antivirus
Be sure to click on the FREE version as they all want you to buy their premium version for $$$.
Select one, download and install. DO NOT install and run more than one, because each on will interfere with the other and slow your PC down badly.
Set it to scan your PC daily, weekly or whenever you choose.
It will do frequent updates to keep the virus list current; this is normal.
DO NOT click on "upgrade" as this will sell you their premium product.
When it finds an infected file, betst to delete it or at least quarantine it so it will no longer affect your PC.
Malware detection programs:
As with AV programs, there are lots. Here are three FREE ones for personal use.
Malwarebytes - http://www.malwarebytes.org/mbam.php
Ad-Aware - http://www.lavasoft.com/single/trialpay.php
Spybot Search and Destroy - http://www.safer-networking.org/en/download/
All the same rules for AV applies here.
Update the malware list each time before you run the scan. Scan weekly or monthly. Delete or quarantine as above.
Regular use of thes two programs will help keep your PC healthy. There is no guarantee that a virus or malware will not sneak in, but that would be rare.