The internal zip drive is a standard ATAPI drive that is used as an internal drive in any PC and available wherever zip drives are sold.
The internal HDD can be either SCSI (50 pin connector) or IDE (Standard  PC form factor). Yamaha has not been able to get Fujitsu brand drives to work.
The following HDD models have been tested and verified to work:
- Seagate ST34311A(4.3 GB)
- Seagate ST36421A(6.4 GB)
- Seagate ST38421A(8.4 GB)
-- Western Digital AC313000 (13 GB)
--- Quantum Fireball CR4.3AT     
--- Quantum Fireball CR6.4AT    
--- Quantum Fireball CR8.4AT
--- Quantum Fireball CR13.0AT
* All Quantum drives should have firmware Version 1.07

RAM can be purchased from our accessory department or at any computer store. Just not the cheap kind. Yamaha manual and literature states:
Expansion memory
(made by other manufacturers)
(use a pair of identical-size 72-pin SIMM modules of the following types)
Access time 70 ns or less
Bit width x 32 (no parity) or
x 36 bit (parity)
Fast Page or EDO,
JEDEC standard
Capacity 4 MB/8 MB/16 MB/32 MB

Internal hard disk drive
(3.5 inch) performance requirements
Interface 50-pin SCSI or 40-pin IDE
Power supply +5V maximum 840 mA
+12V maximum 2400 mA

Internal Zip ® drive
Interface 40-pin IDE (ATAPI)
Power supply +5V 0.8A

Recommended External CD-R/CD-RW Drives
Manufacturer Model Number
Yamaha CRW4416SX
Yamaha CRW6416SX
Yamaha CRW8424SX
Notes
l In order to use the CRW4416SX, the unit's firmware must be version 1.0h = or later, and to use the CRW6416SX, it must be version 1.0c or later. The latest firmware = for each model can be downloaded free from Yamaha's related Web page
ll The CRW8424SX is compatible with A4000/5000 version 1.07 and later. The = update can be downloaded free from Yamaha's related Web page. It is not possible for Yamaha to check all available models of external = CD-ROM drives for compatibility. However, there should be no problem as long as the CD-ROM = drive uses a 50-pin SCSI connection. Internal CD-ROM drives from a PC cannot be used. MO disks = with capacities of more than 640MB cannot be used. However, there is no problem = in using 540MB and 230MB disks with a 640MB MO drive. All trademarks and registered trademarks used herein are property of their = respective holders.