I would first check your adware program logs for information regarding this keylogger. Maybe you'll find clues that will tell you where it came from. Try looking for the first entry or the first time the program detected it. Also, if you know the name of the keylogger use the following command in a dos shell
c:\dir /TC /S keyloggername
This will you give the creation date/time for all the files that have this name. With this information you can start looking for system/application logs that were generated around this date.
Furthermore, if you want, you can use HijackThis (
http://www.trendsecure.com/portal/en-US/tools/security_tools/hijackthis) and post the log for me to analyze.