Failed loading XML file . . .

[omni++]

I have installed Virtuemart into Joomla before without issue.  In this case I am doing a fresh local harddrive server (WAMP) install of Virtuemart 2.0.6 (latest) on a fresh install of the latest / current Joomla, 2.5.4 , using the usual extension install method under Joomla Extensions directory.  All things appear normal in the process except that the install window goes blank and seems to never complete.  Upon refresh Virtuemart is not present.

The platform is Pentium 4 - 1.3Ghz on an Intel motherboard, 768MB Ram, running a fresh install of Windows XP sp3 fully updated.  The machine is dedicated to this purpose with a minimum of other software installed, only that which might in some way pertain to or facilitate Joomla website building.  Firefox 11 is the default browser both in Windows and for WAMP.  Wamp is also the latest available stable download.

Any ideas why Virtuemart does not complete the install will be appreciated.

Thanks !
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Edit - ~17:20 EST :

Tried install via "Install from Directory" which apparently failed also, yielding this message :         

Failed loading XML file
        C:\wamp\www\YDSite1/administrator/modules/mod_atjupgrade/mod_atjupgrade.xml
        XML: failed to load external entity "file:///C:/wamp/www/YDSite1/administrator/modules/mod_atjupgrade/mod_atjupgrade.xml"

[jenkinhill]

Is your local host able to decompress tar.gz packages? Convert to .zip first and try installing that. Also make sure that max_execution_time in your php.ini is set to a high value as I would expect localhost to run slowly on an old system.

The error with Install from Directory is coming from an issue with Joomla's Discover - see https://www.akeebabackup.com/support/admin-tools/10913-failed-loading-xml-file-modatjupgradexml.html