What does Windows error code 7009 (ERROR_CTX_MODEM_INF_NOT_FOUND) mean?

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ERROR_CTX_NO_OUTBUF	ERROR_CTX_INVALID_MODEMNAME

ERROR_CTX_MODEM_INF_NOT_FOUND

The MODEM.INF file was not found.

Windows assigns decimal 7009 and hexadecimal 0x00001B61 to ERROR_CTX_MODEM_INF_NOT_FOUND. The decisive subject is legacy Remote Desktop modem callback configuration; the value alone does not reveal which object, server, file, session, or transition failed.

The native Value is 7009 (0x00001B61). Preserve this result immediately after the failing Windows call because later logging, cleanup, LDAP, RPC, or file operations can replace the last-error value.

Where the result appears

• processing legacy Remote Desktop modem callback configuration.
• applying a user or server configuration that enables the relevant legacy feature.
• handling a session transition or device response in the Terminal Services stack.
• diagnosing a wrapper that translates a WTS or connection result into Win32 form.

State boundary to prove

This result applies to legacy Remote Desktop modem callback configuration and does not by itself prove that the entire server, directory, disk, session, or application is unavailable. The state boundary to prove for this Win32 error is whether the system can locate the MODEM.INF data required to identify and initialize the configured modem. Use resolved MODEM.INF path, Windows component and driver installation state, and Terminal Services callback configuration as independent evidence. When evidence for this Win32 error disagrees, preserve timestamps and investigate the transition instead of selecting the most convenient value.

Likely causes

• the expected modem information file is absent.
• the installation points to the wrong Windows directory.
• legacy modem components were removed.
• file access or servicing left the data unavailable.

Diagnostic sequence

1. capture error 7009 immediately at the API boundary and record the operation that was attempted.
2. identify the exact owner of legacy Remote Desktop modem callback configuration, including object generation, server, path, session, replica, or client context.
3. collect resolved MODEM.INF path before restarting a service or changing configuration.
4. compare Windows component and driver installation state with the documented or observed precondition.
5. correlate Terminal Services callback configuration with TerminalServices operational logs, session and user-configuration records, device or modem diagnostics, and the caller’s connection trace.
6. determine whether side effects occurred and verify recovery after changing one responsible condition.

Evidence to collect

• resolved MODEM.INF path.
• Windows component and driver installation state.
• Terminal Services callback configuration.
• file access result under the service identity.

Correlate this result with TerminalServices operational logs, session and user-configuration records, device or modem diagnostics, and the caller’s connection trace. Keep the first detailed status even when a later wrapper translates it to error 7009; the first status often distinguishes transport, authorization, storage, schema, state, and application-integrity causes that share the same final Win32 result.

Handling, retry, and recovery

The recovery objective is to restore the matching legacy modem components or remove the obsolete callback requirement; do not copy an unrelated MODEM.INF from another Windows build.

Retry it only after the recorded condition changes and completion state is known. Idempotent queries may be repeated after recovery, but mutations require a state check first; backoff cannot repair malformed input, corruption, missing structure, or policy rejection.

Telemetry and support fields

• record ctx_modem_inf_not_found_api for the producing function or management operation.
• record ctx_modem_inf_not_found_target for the file, log, session, replica, object, or server identity.
• record ctx_modem_inf_not_found_state_before and ctx_modem_inf_not_found_requested_transition.
• record ctx_modem_inf_not_found_first_status for the earliest lower-level diagnostic.

For support escalation involving it, retain decimal 7009, hexadecimal 0x00001B61, the API, UTC time, target identity, and first subsystem-specific status. Include the smallest reproducible request and evidence that distinguishes this condition from nearby codes. In the context of it, several modem-related values describe legacy callback functionality. they should be interpreted in that historical configuration context rather than as a generic modern rdp network failure.

Difference from nearby results

ERROR_CTX_INVALID_MODEMNAME means the file was found but the configured modem entry was not present

Practical validation scenario

A preserved Remote Desktop callback policy is applied to a rebuilt server that no longer has modem support installed. Removing the obsolete callback policy resolves the connection setup failure. The negative test should preserve the responsible condition and reproduce it; the recovery test should change only the identified cause, repeat the same operation, and verify both success and the absence of an unintended partial side effect.

Developer and administrator guidance

Administrators handling it should first decide whether the legacy callback or redirection feature is still required. Developers should treat connection-state notifications as state transitions and device failures as component-specific results instead of mapping every value to a generic RDP network outage. Code that exposes it through RPC, JSON, REST, PowerShell, or another protocol should preserve the Win32 domain, decimal 7009, hexadecimal 0x00001B61, and original component diagnostic.

References

• Microsoft: Win32 system error range containing this code — official context relevant to it.
• Microsoft: Remote Desktop Services API — official context relevant to it.
• Microsoft: WTS configuration classes — official context relevant to it.
• Microsoft: WTSAPI32 reference — official context relevant to it.

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