Summary
While trying to load a DPX client onto a Windows machine in which the system drive (usually C:) is nearly full, a message may appear claiming that the computer requires about 450MB of space on the system drive to install. Though the computer may have had more than 450MB prior to installing, the installation process will decrease the system drive's free space by 200-300MB and can leave the system drive with less than the required 450MB. Catalogic Software recommends either removing unnecessary files from the system drive or redirecting some Backup Express resources to another drive.
Resolution
If your Windows system has drives with less than 1GB of free space, especially system/boot drives, it is highly recommended that you clean up these drives and/or move or remove applications to free space in order to ensure stable Windows performance.
That being said, it is possible to redirect some resources such that an install of DPX to an alternate drive does not initially consume space and bring your system drive down below the overall size requirement for the Backup Express installation.
When the Windows product installer starts up, InstallShield references Window's environment variables that point it to locations where it can extract temporary files for the installation process. These can point anywhere, but typically point to temporary folders on your system drive.
To change the location of these temporary file areas, click on My Computer and bring up Properties. Click the Advanced tab and press the Environment Variables button. Under User Variables, change the values for TEMP and TMP to point to a location where the system has more space available in order to extract temporary files for the installation process, as shown in the below screenshot. (Adjust paths as appropriate to your server.)
Note: This does not prevent the loading of DPX components onto your system drive since some required components must be installed onto the system drive. This fix only redirects the temporary file area used by the installer so that it does not interfere with installation requirements.