I've fixed the problem!!
Its a little disappointing when people point the finger at you for not doing UAC and admins. I had read the page stating issues relating to Vista, and followed them before making my post!!
It may also be worth mentioning that I work in the IT industry, and have 13 Microsoft certifications, so I'm pretty comfortable with this.
Anyhow, I have managed to resolve the problem, and I believe this info should be added to the Vista compatability page.
The Knife Edge installer seems to cause a Data Execution Prevention error. You need to therefore either:
a). Note the installer as an exception to DEP protection
b). Switch off DEP whilst you perform the installation
To do this, go to
CONTROL PANEL -> SYSTEM -> ADVANCED SYSTEM SETTINGS
Click the SETTINGS button in the performance section
Select the DATA EXECUTION PREVENTION tab
I selected to effectively disable DEP for the installer, by selecting 'Turn on DEP for essential Windows programs and services only'
Hopefully this will help those folks to get it running on your Vista machine.
Some people may not be encountering this problem because they are running a processor which doesn't support hardware DEP, or maybe they have DEP turned off by default.
Having checked this, it appears that DEP is turned on by default if your processor supports it (as best practice).
I would like to request this be added to the Vista issues page, and I hope it helps!