....and you cannot run the tool without seeing ads.

Not entirely true. You can't run the free version without seeing ads, that's why it's free...

However, you can pay and get an ad free version and that's only $330 per annum. You will then get your own corporate branded version (which some people may want for their organisations anyway).

See http://www.spiceworks.com/myway

I've been using Spiceworks since version 1.6 and it really is turning into a must-have tool.