My computer won't make cache files for large MVS (NeoGeo) roms. Why?

I can make cache files for most MVS games if the roms are like 40MB and lower (the biggest I tried was Last Blade 2 and it worked).

But I want the good stuff like Garou, Samurai Shodown V Special, Rage of the Dragons, KOF 2002, KOF2003, and SVC on my PSP. Whenever I try to convert roms of their size (approx 70MB), the converter will hang at "decrypt gfx" every time.

I have been stumped with this for months and have no idea why this happens with the big roms. I'm using Win98 (yeah, I know...it's old) but there has to be some kind of solution for this, right? Maybe a special plugin for my comp? I know it's not the MVS converter.

Somebody help please >_<