If you know you can trust a program (such as C:\WINDOWS\system32\svchost.exe), then you should tell Comodo to remember your choice. It's far more convenient that way. I would only worry about programs that either (A) you're unfamiliar with or (B) you know you don't want to allow. I don't use Steam on a regular basis, but I do still use it and I have had no conflicts with Comodo. So far, the only thing it's given me trouble with is Battlefield 2142. It takes a day or two to really get used to Comodo, but once you do, you won't want to be without it.