how do I convert Midi to Audio with Digital performer? (its an older version, version 4.1)

For what it's worth i've been waiting until i'm completely done with my composition, running only virtual instruments, rewired synths, samplers, and soft synths, plus any real audio tracks, mixing on the go, and then using a nifty utility called "audio hijack" to record a real time version of the playback directly to an aiff file. bingo there's my mix. my virtual instruments rarely go to audio these days, largely thanks to the increased computing power of the new macs.
I track in DP with my FX plug ins off, low buffer settings for good controller feel, and then bump up the buffer, turn on my power hog plug ins, and mix away. a real time saver for me, it encourages a certain type of work flow, of course, but i'm frequently in a crunch, and sort of enjoy mixing as i go.
my two cents.

I do that too if I don't have to worry about high track counts because playing an audio track is trivial compared to a virtual instrument triggered by midi... sometimes it's best to freeze or render the VI as audio. I know I can play back @ least 100 tracks of audio... I know for a FACT I can't do that with VI's so rendering to audio is the best thing (if your only using 1 machine) now if you have 2 well then time to rip!