Number of tracks is somewhat unpredictable because it depends on many things -- the speed of the CPU, the speed of the frontside bus, the speed of the hard drive, the type of controller that communicates to the hard drive, the amount of RAM you have, the number of other things you are trying to do with the tracks (applying DirectX or VST plug-in effects, for example), how well optimized the entire system is for digital audio recording, and what sampling rate and bit depth you're recording at. Some of the "lite" software versions like Cakewalk Express might also have a limit on the number of tracks they'll support.
When my machine was a Pentium MMX 200 with 64 MB RAM, a 66 MHz FSB, and a 5400 rpm UDMA/33 drive, I could get about five 16-bit, 44.1 kHz tracks before I started having trouble. A P-II 300 would probably get you somewhat more than this... but like I said, an exact number is impossible to predict.