I don't know if I can get any answers because I can't provide much information right now but I want to try. I recently sold old Japanese PC with DTL-H2500, DTL-H2510 and DTL-S2020 installed inside. The PC was already used as base for PS1 dev kit but it came to me without HDD. The guy who bought the set from me now claims that it doesn't work. He got old HDD, installed Windows 98 SE, DTL-H2500 driver from the FD and tries to get DTL-H2500 to work but he says that after he tries h25bios and after it finishes executing, he can't type any other command and he hears just "beep" and nothing on the screen. It's how he described it. Does anybody have any ideas about it? Nothing special installed inside. Just these DTL cards, network card and video adaptor. No AGP slot inside, just three ISA and three PCI slots. Video adaptor is PCI.
There are a few things I can think of - the first is that you don't want any Windows driver installed for the card (it should just show in device manager as 'PCI card') - and make sure it's not conflicting with anything. Depending on how long it's been since it was last used, it's possible it has an old boot ROM image on it and the flash needs updating - IIRC, the tools for this are in the DECI directory of the SDK.
