Older PC, Win98se:
CRT Monitor, PS/2 mouse & keyboard, wireless DSL
Two onboard USB ports, using an extended USB hub
(No printer, scanner or other peripherals)
Had been working perfectly with no problems at all for quite some time.

Moved the CPU to my Daughter's room for her use -
Now:
LCD Flatscreen Monitor, USB keyboard, PS/2 mouse, same wireless DSL
Same extended USB hub
Replaced CD-ROM with a newer CD-R/W

All Power Management set to "never" (shutdown/standby), NO screensaver.

Appears to function perfectly as long as in use.
During a short period of idle (within a 15 min. period) it freezes.

Note: Mouse pointer remains free, i.e., "moves" in an apparently normal sense but with no effect.

Display remains exactly as was/is but frozen as if an image.
No pointer function, hover effects.
No response to the keyboard.
Cannot invoke any processor response/activity at all.

No option but to cold boot.
Once booted, everything is normal again until left idle.

I've not actually "timed" the idle period but it's less than 15 min. that the freeze occurs.

Recap of differences:
Monitor: From CRT to LCD
Keyboard: From PS/2 to USB
Exchange of CD drives

I'm currently at a loss. I'd appreciate any ideas or suggestions.

Any way to add the old monitor, keyboard, and mouse back, one at a time to see if there's ant difference?

Ah, possible yes but with an extreme amount of inconvenience. The old Monitor (17" CRT) is still in use under a new CPU
along with the difference of location (upstairs/downstairs).
I considered this but was saving it as a 'Last Resort'.

I was hoping this was a "not-so-UNheard-of" issue that someone might have an idea what was causing it.