I had the same error as well when trying to install iCloud for control panel, good thing i came across your post.
So before taking your advice and restarting my computer, i decided to try install it again and it worked the second time round without a hitch.
I reckon however that restarting would be a good solution for anyone else who encounters this problem.
When trying to install iCloud for Windows in Windows v8.1 64 bit I get the error:
"The installer encountered errors before iCloud Control panel could be configured. Your system has not been modified. To try these operations at a later time, please run the installer again"
I have disable the Anti Virus, removed other Apple apps, re booted the system and have tried the installer several time from several sources. THEY ALL FAIL.
Excerpt from Event Viewer;
Product: iCloud -- Error 1722. There is a problem with this Windows Installer package. A program run as part of the setup did not finish as expected. Contact your support personnel or package vendor. Action RuniCloudUpgrade, location: C:\Program Files (x86)\Common Files\Apple\Internet Services\, command: C:\Program Files (x86)\Common Files\Apple\Internet Services\iCloud.exe /upgrade
My stystem does not have a C:\Program Files (x86)\Common Files\Apple\Internet Services floder