Thanks Bricat,

I ran the Malwarebytes' Anti-Malware and the report is posted below however Sophos Anti-Rootkit says it doesn't currently support Vista so will not run.

Malwarebytes' Anti-Malware 1.11
Database version: 710

Scan type: Quick Scan
Objects scanned: 36552
Time elapsed: 16 minute(s), 29 second(s)

Memory Processes Infected: 0
Memory Modules Infected: 0
Registry Keys Infected: 1
Registry Values Infected: 0
Registry Data Items Infected: 0
Folders Infected: 0
Files Infected: 0

Memory Processes Infected:
(No malicious items detected)

Memory Modules Infected:
(No malicious items detected)

Registry Keys Infected:
HKEY_CURRENT_USER\Software\Trymedia Systems (Adware.Trymedia) -> Quarantined and deleted successfully.

Registry Values Infected:
(No malicious items detected)

Registry Data Items Infected:
(No malicious items detected)

Folders Infected:
(No malicious items detected)

Files Infected:
(No malicious items detected)