If you updated Windows Installer
Each Vista download says that it is not for my system. I guess I'm already updated? performed a customized installation without Ad-Watch, then manually installed the Ad-Watch driver afterwards
I performed the customized installation without Ad-Watch but the installation did not finish so I did not install the driver afterwards - and it didn't work - perhaps you should try a clean install.
Installing on top of old versions doesn't work well since the uninstaller does a poor job. At
this thread you'll find links to Windows Installer Cleanup Utility and Revo Uninstaller which will help you do a clean uninstall of all Lavasoft/Ad-Aware junk on your PC.
The Windows uninstaller does not work I get this error-type message: 
I instead turned to Revo and deleted what it found, retried the install, and it still did not work.
Then download a fresh copy of the installer from
http://lavasoft.com/products/ad_aware_free.php and save it to your hard drive. When you install, it's best to stop all applications/processes to avoid any conflicts.
Didn't help at all.
If a clean install doesn't work, there's a possibility you're infected with something which prevents Ad-Aware from properly installing. In that case, read the instructions in my signature:
1. post a log in the HijackThis forum. Copy/paste or link to this thread to describe the problem, and somebody there can help you with malware removal.
2. submit malware to Lavasoft for analysis - this will help in future definitions and software updates
I followed the instructions but ERUNT is for XP, not Vista. Is there a similar program I can use?