We have found three things that might provoke this kind of behavior:
1) You have the Yamaha SoftSynth installed. For reasons yet unknown - both Propellerhead and Yamaha have investigated this - these programs, or parts thereof, conflict with each other and if you have the SoftSynth installed ReBirth just won't run.
2) You have a Virtual CD driver installed. We have found that Virtual CD (a small program that 'tricks' your computer into believing that a part of your hard disk is a CD-ROM drive) conflicts with ReBirth, you can't get ReBirth to run if you have it installed. Uninstalling Virtual CD won't do the trick, however, since it's still there in the Windows registry, from which it must be completely removed before ReBirth will run.
3) Your computer is too slow! This problem is very difficult to identify, since it relates to so many factors. The clock frequency is not the only thing; some can get ReBirth to run OK on a Pentium 90 while others say that it hardly works on a Pentium 166MMX. You may have peripherals, odd system extensions or inefficient sound drivers that slow the system down.