How do you direct mame to the correct file to access your rooms from that folder?
Open up mame.ini (should be in same folder as mame.exe).
Open it with notepad or word.
Make sure the paths are correct.
Here is an example in my mame.ini file (It may be called .cfg)
### Windows path and directory options ###
rompath C:\Arcade\Mame\Roms
samplepath C:\Arcade\Mame\samples
inipath C:\Arcade\Mame
cfg_directory C:\Arcade\Mame\cfg
nvram_directory C:\Arcade\Mame\nvram
memcard_directory C:\Arcade\Mame\memcard
input_directory C:\Arcade\Mame\inp
hiscore_directory C:\Arcade\Mame\hi
state_directory C:\Arcade\Mame\sta
artwork_directory C:\Arcade\Mame\artwork
snapshot_directory C:\Arcade\Mame\snap
diff_directory C:\Arcade\Mame\diff
ctrlr_directory C:\Arcade\Mame\ctrlr
cheat_file C:\Arcade\Mame\cheat.dat
Make sure that the paths are correct on your computer. If you just copied everything from your dads computer, chances are good that the paths are not the same on your computer.