Well... some more results.
Tried to boot Demo CD on my old ASUS A7N8X-E DeLuxe (Athlon XP 2600+) but no luck on any mode (Modern, Modern with /VW, Safe mode, Legacy...). In fact, the boot always start as it should but after loading LOCATECD.SYS the boot process proceeds in such a slow pace that I was not in the mood to wait it finished (almost 5 minutes just to load the first 10 drivers.
Oddly enough, this system runs flawless eCS 2.0 (and also every older version of OS/2).
Booting on my "new" Intel DH67CL motherboard (i7 processor) seems to be improved compared to previous versions of eCS and OS/2 (which simply gave me a trap even before showing boot logo): now it boots to the options menu and then it proceeds to the system boot. It is very nice to see it running... but it "hangs" on network card "configuration" screen. Probably it is waiting for some key, but this is an impossible action, since it seems my USB keyboard is non operative. This "new" machine (which I bought two years ago, when I bought my eCS 2.0 license too) has no PS/2 or serial/keyboard ports... it has USB (EHCI) ports only. It is sad I was never able to run OS/2 nor eCS on this machine.
(I always took care of buying hardware that supported OS/2... every "external" device on these computers are supported; I just never thought that a motherboard could cause so much trouble when booting an operating system).