There is no 'HKCU\Software\Acronis' key.
The key is located in 'HKLM\Software\Acronis' (probably because Acronis was installed via Acronis remote console).
Accordingly with your detection rule, you can run CCleaner with any administrator, Acronis is nerver found.
Any other suggestionS?
Thanks,
Michel
PS: Forget my remark about W2K, Acronis was installed manually so there is a HKCU key.