Still using Windows XP?
Are you using Internet Explorer?
Don't do that.
My friends will laugh and say I have always hated Internet Explorer. I really do dislike "IE". I have been steadfastly using Firefox since it was introduced. Internet Explorer just felt slow and bloated and generally "icky".
I have an XP machine here at the house, and there are people in Corporate environments who still use XP. It's around 1/3 of the PCs out there at this point and declining.
The problem is that there's a security change coming down the pike that will make Internet Explorer on Windows XP less secure.
The quick solution is to always use a different browser when you can. I suggest Firefox, but Chrome as well will work. The security change that you need is in the more modern browsers and Internet Explorer is not being kept up to date by Microsoft on Windows XP.
If you want the long story, you can follow this link to Naked Security.
Bottom line is it's time to change your browser or upgrade the computer to run Windows 7.