Microsoft is warning users of a potential issue in its upcoming Internet Explorer 8 (IE8) web browser release that makes it impossible to revert to an older version.

The company said in a blog posting that users who were running Windows XP Service Pack 3 would be unable to remove the browser and install a previous version.

The issue arises when a user installs the SP3 update after having previously installed the first beta release of IE8. Upon attempting to install the recently released beta 2 version of the browser, the user will be left unable to revert either IE8 or Windows XP to any previous release.

Users will still be able to install future updates, and the company said that the problem only arises when the user has installed XP SP3, after installing the first IE8 beta.

To avoid the issue, the company recommends that XP users who have installed SP3 after the IE8 beta 1 release manually uninstall the browser.

Users running Windows Vista, Server 2003 and Server 2008 are also being advised to manually uninstall the first IE8 beta before updating as well, though those systems are said to not be affected by the downgrade issue.

Microsoft released the second beta version of IE8 yesterday. The new incarnation of the browser has built-in malware support and a privacy feature designed to protect a user's browsing history and cookie data.