Intel® Pentium® II 450MHz, AMD Athlon® 600MHz or faster processor (or equivalent)
Today the requirements for Flash 10.3 are:
Intel Pentium 4 2.33GHz, Athlon 64 2800+ or faster processor (or equivalent)
This most certainly means that a CPU supporting SSE2 instructions is now mandatory for running the latest Flash 10 builds whereas the earliest ones didn't even require CPUs having SSE support, Athlon 600Mhz having only MMX and 3DNow. I think you've got to find the most recent possible Flash 10 compatible with your CPUs on OldApps, FileHippo or any other similar website.
I might be wrong though but you'd better try that first and then report whether you can run earlier Flash 10 versions or not.
Edited by loblo, 16 June 2011 - 01:50 AM.