Your muscles need at least one day of rest in between workouts. So if you're doing a split routine (lower body one day, upper body the next), then it's fine to do strength training 5x/wk. If you're doing a full-body routine, then your best bet is 2-3x/wk. The frequency isn't necessarily as important as the intensity of the routine. You should be lifting to fatigue (meaning that the last rep you do in the set is the last one you can do in proper form), typically in 1-3 sets with 8-12 repetitions per set.
Unless you're a bodybuilder or focusing on bulking up, split routines aren't really necessary. You can get good results from a full-body routine just a few times a week.
Hope that helps,
"You may have a fresh start any moment you choose, for this thing that we call "failure" is not the falling down but the staying down." Mary Pickford
"No matter how slow you go, you are still lapping everybody on the couch."