I recently wrote up a procedure for a colleague having problems with Adware. I am posting here for my own reference. YMMV; no warranty expressed or implied.
There are 2 kinds of malware that you need to be concerned about – adware and spyware.
Here are some articles about removing them: This one is about removing Adware from Google Chrome. Ignore it if you are using a different browser. This is a Spyware removal article from PC World. You should read it, but not necessarily follow the instructions.
My first suggestion is to make sure your anti-virus on your computer is up to date. If you don’t have an anti-virus program, the first thing you should do is download Microsoft Security Essentials and install it. It’s free, it’s from Microsoft, and it works as well as any of the free anti-virus programs out there.
Once your anti-virus is up to date and you have scanned your computer, I recommend moving on to Ad-Aware. For Ad-Aware and the rest of the following programs I recommend in these instructions, make sure that you “un-check” any additional software that may be piggy-backing with the free software. This can be other anti-virus programs, pdf programs, video programs, etc. The software publishers include these to allow them to offer their free versions, but the reputable publishers allow you to opt out. AFAIK, there are not any surprise programs installed with anything I recommend here.
If the problem persists at this point, there is other software available for removing Spyware/Adware/Malware. I suggest trying them in this order:
Give each program time to solve the problem. (Intall, scan, run the computer for a day or 2). If it solves the problem, keep it. If it doesn’t, uninstall the program, (but always keep an anti-virus program such as Microsoft Security Essentials on your computer).