Windows Vista Upgrade Advisor
Full user review
"Good for a guide, but certainly not perfect."
It identifies hardware the computer contains that might not work, because some of it will work anyway with some adjustment. For instance it said the Broadxent internal modem on older socket 462 mobo wouldn't work under Vista. True, to a point, the installation program wouldn't run since it realized Vista was not W2K. It did install the driver files and the modem work fine simply by right clking on the install file, choosing properties, then the compatibility tab, and setting to W2K, which was an NT system too. Install program ran fine then, loaded the driver files, and Vista had no problem running the old dialup modem. So, use it as a guide, not as the final word on what will or not run under Vista.
Doesn't determine if hardware it says won't run Vista will be able to do so using Compatibility Mode.
Like any tool, it's value is based on the ability of the user.