The problem, which I personally experienced was that when my NOD32 antivirus was giving me a notice saying that I have to perform my Windows XP update. By clicking on the link for the update, an empty Internet Explorer page popped out with an address http://windowsupdate.microsoft.com/. Refreshing that page didn't give any results - the window was empty. There might also be several symptoms, such as blank page on windows update, unable to start system restore, web pages aren't displaying properly, some applications aren't working correctly, etc. To fix this, open your command prompt (click
Start -> Run, then type
cmd) and enter following commands:
regsvr32 /i mshtml
Confirmation windows might pop out. Close Internet Explorer and then try opening the update page again, it should work now.