I found a way to do this, buit it is not really a clean install. I
copied Windows Vista files to another drive (e.g., USB HDD) in Windows
XP. I ran its setup.exe.

It gave me two choices: Upgrade or custom. I didn't want to upgrade so
I picked custom but there is no clean install from scratch. It would
only rename and move my old Windows folder and files. I do not want to
do this. I was to format/erase C: drive and install Vista.

I also see this behavior in Windows 7 beta builds.


I have an old Dell Dimension 8250 test PC that I would like to install
Vista onto. However, it has no DVD drives. I cannot even boot from
external USB drives (3.5" disk drive, external HDDs, and DVD burner
drive -- CMOS doesn't see them and found out PC doesn't support bootable
USB devices).

However, I do have enough HDD space (30 GB free on second partition) to
copy Vista DVD (or make an ISO file) onto it through network (will take
a while).

Thank you in advance.