I downloaded Architectural Revit 2012. I had 8.5 Gb of free disc space to work with. While installing I got an error and found I was out of disc space. System requirement was 5Gb free disc space required, any ideas why this happened?
Have you tried posting in the installation forum?
http://forums.autodesk.com/t5/Installation-Licensing/bd-p/24
LD
You will need at least twice that much as it will need to expand the download and then install it, effectively doubling the amount of space the actual program takes. You should clear out some more space or move some of your larger files to another hard drive or resource.
If you do not have a location to archive files, consider temporarily reducing your virtual memory swap space and deleting everything under your %temp% and %systemroot%/temp locations. You might also consider burning your extracted installation files to DVD and installing from there.
For faster responses concerning Autodesk installation issues, please post your questions in the Installation and Network Licensing user forum here:
http://forums.autodesk.com/t5/Installation-Licensing/bd-p/24