Calibre will not install

Hi Kovid, the latest version of Calibre will not install. It should have installed over the previous version on my D drive. I get the message:

Out of disk space
Volume Disk Size Available Required
C: 99GB 455MB 719MB
D: 931GB 602GB 0KB

You will see that I have plenty of room on the D drive.

How can I persuade the MSI to use D instead of C for the install?

Cheers

Paddy