To add to the above post, you can grab a tracking conversion pixel from Google / Yahoo or whatever network you are buying traffic from. This will show you conversions on a per AdGroup level. The tracking pixel will help you determine which ad groups perform the best.
Also, don't pass the keyword to the Affiliate Network. The only person that should see that information is YOU...so you could do one of two things:
You could make your own Excel spreadsheet:
keyword 1 = 1
keyword 2 = 2 etc...
Or -
If you don't want to do that (and I don't recommend you do) - code your own tracking system or setup a system like
http://prosper202.com on your own server. Prosper202 is free and its relatively easy to setup, and you can track keywords/subids/and get a tracking pixel to give to the network (or place yourself if that network allows it). The purpose of the tracking pixel will help you find out which subid's converted by passing a number to the affiliate network rather than a keyword. Since only you have access to Prosper202, you'd be able to pull a subid report at the network - see which SubID's converted, and then upload those subid's to Prosper202. Prosper202 will then tell you which ads/subid's converted.
If all else fails and you don't care about passing the keyword to the network, you can simply ad a number in front or behind the keyword and that will help you differentiate between links/ads. something like this: cpanetworklink.com/youraffid/{KeyWord:default}ad1 and cpanetworklink.com/youraffid/{KeyWord:default}ad2
etc.