|Certain web pages may re-direct to another web page if you are using an older address that's no longer valid, but if it is re-directing other than that.....|
You probably have malware (most malware these days is NOT a virus).
Do a full scan of at least your partition Windows itself is installed on, which is usually but not always C for XP, with whatever anti-malware program you have installed.
(If you go to Start - Run - type.. cmd, click OK or press Enter, whatever the drive letter is at the beginning of the resulting line is the drive letter of the partition Windows itself was installed on.)
If that doesn't find whatever is causing the re-direction, download the free version of Malwarebytes and do a full scan, and have it remove everything it finds.
If you have lots of symptoms that you haven't mentioned, see this to see if it applies:
"Rogue" anti-malware program, run Malwarebytes
See response 1: