I get asked sometimes to provide a document that help desks can use to troubleshoot various Citrix Receiver issues on the Windows client PC. Some of those issues might be failed installs, failed uninstalls, failed upgrades, registry corruption, or all of the above. Here is a basic process that should address most of these:
1). Uninstall Citrix Receiver using the Wizard.
2). If uninstalling fails, or if a future install fails due to components still stuck in the registry, run the cleanup utility: http://support.citrix.com/article/CTX137494
3). Reinstall Citrix Receiver
4). If failures still occur, run the Citrix diagnostic tool in order to collect data and upload it to Citrix for analysis: http://support.citrix.com/article/CTX141751
5). If all else fails (or if time does not permit to wait for Citrix to analyze logs and respond), re-image the client PC and start over with a fresh image.