I know on my Dell Axim X51v (WM5.0) that programs are installed on the ROM so that when the battery is lost, the programs aren't.
I know on my old iPAQ 1945 (WM2003) that programs are installed to the RAM... and that in the event that there is a battery loss... the whole thing is lost.

Is storing the programs on the ROM a WM 5.0 feature or a device-specific feature?

Cry “havoc!” and let loose the dogs of war,
That this foul deed shall smell above the earth
With carrion men, groaning for burial.
William Shakespeare (1564–1616), british dramatist, poet.

WM5 is based on persistent storage. No option to store programs in RAM (beside RAM-disk)