This is most dependent on the HD subsystem (controller/HD).
Other factors might influence the track count before fart-out but the main one is the HD.
The Echo reporter is a good ballpark estimate but:
The best way to know when you are approaching the wall is to just test it and find out. Record a minute or so of some sound and save it as a .wav file at the resolution you intend to use for recording. Then copy this file repeatedly and save each clone with a separate name (test_track_1, test_track_2... etc.) until you have a shitload of 'em. Then drop, say 16 of 'em into your CW project and hit playback. No problems? Add another.
Rinse and repeat until the playback stutters.
You might be at this a while: My PII-450 made it to 36 before it farted out.
And of course, added effects chains will add to the overhead so you might want to include what you normally use for a more realistic appraisal. Reverbs can be a track-count killer.
