Premiere needs to have the focus for playback, because of the resources it needs. If it no longer has the focus, as in the situation you describe, playback is stopped. That is by design. Use WMP or similar player if you want to hear the audio while surfing.
The 2 second lag is probably caused by background processes. Check with Process Explorer and if you have more than 40 to 50 processes running, you should tune your system and kill more processes.
I recommend using a separate computer for tasks like web surfing, email, and music. Those applications can be run on an inexpensive, older computer. Doing so can allow you to do all sorts of things better with your editing workstation---including disconnecting it from the Internet and turning off antivirus software (which can cause performance problems).
Thank you both for the reply,
Okay, so the lag issue. Todd, I did try all the stuff you said. I turned off many proceses, made sure nothing un-needed wasn't on in the compuer start up. Closed all apps, etc. WHen i check Task manager, it says I have 0 cpu usage, and 2 gb ram in use. Then I open premiere and do a test project with only one small audio file. It lags approx 2 seconds after I hit play, before it actually starts playinmg.
I don't see what else I can do?
I noticed this lag as well and was just going to ask about the lag on play start. I see no answers though from your post.
Hmmm. Ideas beyond this?
Your first problem can be solved by upgrading to CS6.
Regarding lag, what is the file type? MP3?
h264 dslr footage from canon