I downloaded the file com_virtuemart.2.0.0_extract_first.zip to upgrade my current version, I unzipped the files and uploaded both to my site, now in the back end of my Joomla based site and I click on virtuemart in the components list I get this message........
Fatal error: Cannot redeclare class vmRequest in /home/as****55/public_html/administrator/components/com_virtuemart/classes/request.class.php on line 597
Line 597 class vmRequest extends vm_vmRequest {}
http://forum.virtuemart.net/index.php?topic=95208.msg312516#msg312516