To reduce disk space used by Vista installation:
use
vLite to clean unneeded features from Vista installation.
With removing speech recognition, unneeded language support, unneeded drivers ect. you can save about half the space for Vista without losing important features.
you can also preconfigure vista installation, slipstram updates and many things more. Read online tutorials and discussions on
neowin.net and
msfn
To speed up Vista:
Reducing disk space used by Vista with above method will also speed it up a bit, but there are a lot more things to do with or without reducing size.
Enable logon as "REAL ADMINISTRATOR" and delete all other user accounts you can delete will speed it up and reduce size. Security will be lower, but if you have good AV software as AVG and SpyBot installed, who cares.
Disable UAC (User Account Controll)
Disable ShadowCoping on all drives.
Disable LAST ACCESSED timestamp for all files
Those are the tweaks i use as mandatory for all configurations even the best one.
(to regain security on better configurations i use additional external software in rare cases)
Using the tweaks above you'll gain in response time about 100% by skipping idiotic vista dialog boxes and such (UAC). (What would happen if Microsoft was making cars? When you kick brakes, the car would ask you: Are you sure?"...)
You'll gain in disk read and write speed simply by reducing redundant data on the disk and redundant data writing (shadowcopy and last accessed timestamp) and removing eg. retarded and inefficient, memory resident system virus protection as windows defender (use eg. AVG and SpyBot instead).
Anyway, what i've written here is not very useful to anyone, but with the above as a hint and a lot of googling around you'll finally end up with the system performance at maximum and only boundary will be set by your hardware.