With the Z80 (unless they have changed since I used them) you will need external memory for the program to be stored in. Dallas had a DS5000 way way back that had a serial loader and memory in it. I think I actually still have a couple in a box somewhere. Anyway, you did not post what you have so I assume you just have a Z80 chip? Hyperterm is an terminal program, so you would need some type loader to dump hex in to in.
You might want to check out microchip.com, get samples and play with them as they have RAM and ROM inside of them and many other peripherals, you will need to make a programmer as well.
If you google or search the forum "here" you will find a Nigel Goodwin and Bill (Blueroom Electronics) that have about everything you need to get started on a low budget. Tutorials to programmers.
Also download MPLABs from microchip.com as well.
I don't have a loader. I'm trying to find one. I have assembled some code with TASM assembler, and I need to convert to HEX and find a loader to load the HEX in.Do you have to dump hex in it. Like the old Motorola and Intel formats? In the old days we made the obj/binary file, then had to bin2hex (convert it to a formatted ascii file with address, byte count, bytes and checksum) and transmit it in ASCII to the loader.
You really should look into the PICs, a lot more fun and a lot less money and headache.
Is your Z80 talking to the PC OK and you just can bot get your code loaded? Hyperterm is the worst dumb terminal program, maybe get procom or something else. Where are you getting stuck. Any info on the loader?
You either have a ROM monitor on a boot loader of some sort.
When you power up the Z80 system does it spit out anything over the serial port. Do you know what baud rate it uses. 1200 and 9600 were popular.
Yes I have a powerup message displayed while in Hyperterminal. the bootup code has the USART at 2400 baud