With Nero 126.96.36.199 on Windows 98 (first edition), it won't let me run a simulation unless I turn off SMART-BURN. Turning off SMART-BURN limits write speed to 16x. The burner is a LTR-32123S, which has firmware XS0Z.
Interestingly, it would let me run a simulation normally on my LTR-48125W, but I replaced it with the 32123S because the computer is too slow to burn faster than 32x, and I have a faster computer that can burn at 48x. When I replaced the burner, I un-installed the version of Nero that came with the 48125W and installed Nero using the serial number that came with the 32123S.