Slow launch of applications

It takes sometimes a minute or more to launch Mail, Safari, etc. Office also very slow. Icon just keeps bouncing until it finally loads.

Have purchased more RAM (now 8 GB with plenty of room, as well as on hard disk), fixed preferences/did disk utility, don't have MacKeeper, done the disk hardware analysis (reboot with control-R), all to no avail. I do have Content Barrier, but still slow if disabled. Did migrate from a PowerPC G5 years ago, but more for just archived documents and do not use them. Would not know how to find and remove any programs still running from there anyway (articles to help say to avoid migrating, etc, but not on what to do if you already have done this). Don't have anything special as this is just a home computer for a non-technical person.

Any thoughts?

Thanks.