I'm trying to use 32-bit registers since I need a bigger maximum integer value. When I try to use EAX, EBX, ECX, or EDX, the TASM says UNDEFINED SYMBOL. TASM is reading the registers as variables. Do know the reason why? I'm using the DOSBOX 0.74 and running on Windows 7 64 bits.
TASM as in Borland Turbo Assembler? I'd be surprised if something that old even knew about 32-bit registers :-)
TASM v5 was from about 15 years ago.
From memory, there was a TASM32 (this may be part of your package) which could do this but I'd suggest getting a more modern assembler, like nasm.