Basic suggested DIY steps to defend your Windows computer:
Stay up with the following:
Windows® Updates, Java® Runtime Environment, Adobe® Flash Player, Adobe® Shockwave, and Adobe® Reader. (Antivirus needs to stay updated, but that goes without saying.)
If your system is not periodically recommending that you update these components you should manually download and install the latest versions.
These updates can be accessed here:
Windows Update http://windowsupdate.microsoft.com Download and Install
The Java Runtime Environment and several Adobe components are used by many web sites.
Java Runtime Environment, http://www.java.com/en/download/manual.jsp
Adobe Flash Player, http://www.adobe.com/support/flashplayer/downloads.html
Adobe Shockwave, and http://get.adobe.com/shockwave/
Adobe Reader. http://get.adobe.com/reader
These modules and subsystems are constantly being attacked by the bad guys and the vendors are always playing catch-up to plug security holes.
Side notes: Windows should be updated to the latest Major Patch Release:
Windows XP SP3 is the latest major XP patch level – This is a large download.
(Manual Download Here: http://www.microsoft.com/downloads/details.aspx?FamilyId=5B33B5A8-5E76-401F-BE08-1E1555D4F3D4&displaylang=en )
Windows Vista SP2 – This is a large download. and the install can take as long 2 hrs+ with multiple reboots during the process. If you manually download make sure you download the correct version x86 (32-bit )or x64 (64-bit).
( Manual Download Here: http://support.microsoft.com/kb/935791 )
Internet Explorer 8 notes – You should be using Internet Explorer version 8
( Manual Download Here: http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=341c2ad5-8c3d-4347-8c03-08cdecd8852b )
Caution this download can cause problems for some other application programs. If it does, Google the offending 3rd party application and see if there is a patch for Internet, if so install it. If it does not resolve the issue uninstall Internet Explorer 8 (Control panel->Add Remove Programs(XP)). Also note that the 64 bit Windows versions need a different IE8 install program. Google it.
Other browsers ie: Firefox, Chrome, Safari, Opera, … should be kept up to date.
Verify that Antivirus/Antispyware(AV) is up to date (and not expired).
Your AV software should be updated and used for a full scan at least once every 2 weeks.
Any problems, consult a professional. Problems in any of these areas should be addressed and not ignored. Things will only get worse over time.
Note that if you are on a dial-up link the download of any updates could take days and may never complete successfully.
Disclaimer: The information and opinion presented above is not warranted for correctness, completeness or applicability to every circumstance. Attempting these updates can impair or impact system function in a negative way, including complete loss of function (rare). No claim is being made that these steps are guaranteed to prevent all perils, additional precautions and steps may be necessary, especially if an infection is already at work on your system. The suggestions offered herein are provided only as basic prudent steps to reduce risks of malware infection. In every case it is recomended that a reboot /restart be done following each download/install step.