What did you install or download that corresponds with the date you started having this anomaly?
The first thing to do is run a couple of on line scans to see if your computer is infected with either a virus or malware:Web based online Antivirus and anti-malware scans:
(these can be run regardless of whatever else you are using. You must use Internet Explorer to run these.)
Panda Activescan http://www.pandasoftware.com/activescan/co...n_principal.htm
Trend Micro antivirus and malware scan:http://housecall-beta.trendmicro.com/en/st...orp.asp?id=scan
Etrust Anti-virus web scannerhttp://www3.ca.com/securityadvisor/virusinfo/scan.aspx
Kaspersky Anti-Virus Web Scannerhttp://www.kaspersky.com/service?chapter=161739400#betatest
Set these to be allowed to fix whatever they find.
The next step would be to download and use several anti-malware programs.Anti-malware freeware
(You can run as many of these as you wish. Generally there is no conflict between these and you should always run several)
Microsoft Antispyware Beta: http://www.microsoft.com/athome/security/s...re/default.mspx
Spybot S&D: http://www.safer-networking.org/en/index.html
Microsoft Malicious Software Removal Tool (Win XP and Win 2000):http://www.microsoft.com/security/malwareremove/default.mspx
Zerospyware (recommended by Microsoft Security) Windows 98/Me/2000/XPhttp://www.download.com/ZeroSpyware-Limite...feed&jump=winmp
CWShredder from InterMute
CW Shredder removes some variants of spyware known as the Coolwebsearch Trojan. The Trojan takes advantage of a flaw in a key component of Windows -- Microsoft's version of the Java Virtual Machine -- to install itself via popups often found on porn and illegal software (a.k.a. "warez") sites. Run CWShredder after installing, and have it look for updates. Then click the "Fix" button, and the program will both scan and fix any problems it finds. If your system does not have this kind of spyware, it will give you the good news.