Sharing this in case it helps someone else dealing with high CPU usage on an RDS server.

We occasionally see Remote Desktop Servers hitting 70–100% CPU usage, and it can be tough to track down the cause.

Quick Tip:

If you can identify the culprit process, you can right-click it in Task Manager > Details tab > Set Affinity, and assign it to just one CPU core. This can instantly improve server responsiveness, giving you time to troubleshoot properly.

But recently, we had a case where CPU usage spiked and none of the usual tools—built-in or third-party—helped pinpoint the issue.

The surprising cause?

A corrupted user profile.

After trying everything else, we decided to log all users off and have them log back in one by one. The moment a specific user signed in, CPU usage spiked. The weird part? No apps were even running under that session yet.

The fix:

1. Log off the affected user.
2. Rename their folder in C:\Users (e.g., jdoe → jdoe_old).
3. Open Registry Editor and go to: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList Find the key corresponding to that user’s SID and delete it.
4. Let the user log in again – Windows will create a fresh profile.
5. Optionally, copy needed data from the old profile to the new one.

After this, CPU usage stayed normal and the problem was gone.