Windows Installer for SRM 7.6

I am just about to upgrade our BMC Service Request Management 2.2 patch 4 to SRM 7.6 patch 1. It should be a straight forward upgrade. I will install everything on the D-drive and I've deleted stuff so I have at least 2 GB free space. On the C-drive we have only the Windows operating system and we are not allowed to install anything else on the C-drive.

I start the installation but it halts before the actual installation starts with a message that I need to free up space on the C-drive for temporary 1500 MB data and it is only 1376 MB space available.

WTF! I have nothing to free up on the C-drive. Can't I use some network drive for temporary storage during the installation? Or use the 8GB memory that is mostly unused at the moment? Quite often I wish we were using Unix/Linux instead of this toy-OS called Windows.

See you later... now I have to call some Windows-tech to help me expand the C-drive or whatever they do.