There are few windows choices available. Copernic is arguably the best third party desktop search for windows (that uses indexing). I admit that I used to like Copernic much better back before they split the product into 'Free', 'Pro' and 'Corporate'. Now you have to pay for the 'pro' level to get network HDD search.
Super Finder XT is a free tools that has been updated to give a 'Ribbon' similar to Office 2007. It's a fast indexer, has a reasonable memory footprint, can integrate with the explorer & has documentation in many languages. Honestly, I can't remember if you can see the file contents when running your search.
A tool that I have not used, but have heard people talk about is Exalead. It used to be a commercial-only product, but now comes in a free edition. I have no idea if you can tune the indexing the way you are asking.
Depending on how important this feature is to you, you may consider an upgrade to Windows 7. The desktop search included with the OS is a far cry from the horribly broken search that used to be the windows standard - good enough that you probably would not need a third party desktop search. I admit to not being a windows 7 search expert, but the few times I've used it it's a major upgrade from Windows XP.