Seattle, April 13 (Reuters): Microsoft Corp. yesterday warned of five new ?critical?-rated security flaws in its Windows, Internet Explorer, Word and Messenger software programmes that could allow attackers to take control of a personal computer.

The world?s largest software maker issued software patches to fix the problems as part of its monthly security bulletin, which included three other security warnings, rated at the second-highest level of ?important.?

Computer security experts urged users to download and install the patches, available at www.microsoft.com/security.

?Anything that?s rated as a critical has the risk of someone being able to take over that machine completely,? said Michael Sutton, director at iDefense Labs, the computer security company that worked with Microsoft to uncover three of the new vulnerabilities.

In addition to the vulnerabilities affecting Windows, Internet Explorer, Word and Messenger, Microsoft also issued a warning about a flaw affecting its Exchange Server software, used on networked computers.