For some reason, your registry on that machine is in a bad state.
If your machine has iCloud version 5.1.0.34 installed (you can check the version of iCloud installed at Control Panel\All Control Panel Items\Programs and Features) and iCloud 5.1 keep showing up on "Apple Software Update" on your Windows machine, then follow the following steps to fix the problem:
1). Update to iCloud 5.1
2). Run regedit
3). Go to: HKEY_CLASSES_ROOT\Installer\UpgradeCodes\0C02866596E20E1128D16590FD7D0258
4). Keep "(Default)" and "A22E84B40BF2AFE49BE959B4E105DC96", but delete everything else (other keys).
And this will fix up your registry and the problem.