New CD-RW installed, existing CD-ROM stops working — What should the customer check first on IDE/PATA systems?

Introduction / Context:
On legacy IDE/PATA channels, two devices share a cable and require proper role assignment. Installing an optical drive with incorrect jumpers often causes both drives to disappear or one to stop functioning.

Given Data / Assumptions:

• System previously worked with a CD-ROM.
• A new CD-RW was added to the same IDE channel.
• After installation, the old drive no longer works.

Concept / Approach:

Each IDE channel supports two devices: one Master and one Slave (or both Cable-Select with a CS-rated cable). Conflicting jumpers or mixing CS with fixed roles breaks device detection by the BIOS/OS.

Step-by-Step Solution:

Verification / Alternative check:

Motherboard and drive labels/silkscreens show valid jumper configurations; correcting them typically restores operation without firmware changes.

Why Other Options Are Wrong:

BIOS flashing is unnecessary for simple detection conflicts. CONFIG.SYS is not responsible for hardware enumeration on modern Windows. Adding devices manually rarely fixes physical role conflicts.

Common Pitfalls:

Leaving both on Master, mixing CS with fixed roles, or using a non-CS cable with CS mode.

Final Answer:

Verify jumper settings (Master/Slave/Cable-Select) on the new CD-RW.