PC & Laptop Repair CD on ebay

PC & Laptop Repair CD on eBay has anybody actually used these?
Do they work?
What are their limitations?
Here is a example http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=220335720063
I am not the seller, this is just a example.

If I have a windows license key where do I find windows o/s system that I can download?