Naomi and K9 are good alternatives.
If you really want to use a keylogger, and you're SURE it's not infected and it's a serious application, you can use the two Exclusion lists in avast:
For the Standard Shield provider (on-access scanning):
Left click the 'a' blue icon, click on the provider icon at left and then Customize.
Go to Advanced tab and click on Add button...
For the other providers (on-demmand scanning):
Right click the 'a' blue icon, click Program Settings.
Go to Exclusions tab and click on Add button...
You can use wildcards like * and ?.
But be carefull, you should 'exclude' that many files that let your system in danger.