Hi,
To uninstall SEP client you can choose any of the following method.
1) Add/remove programs - Not working in your case
2) Manual uninstall process - It can be time consuming process.
Manual uninstallation documents for Symantec Endpoint Protection
http://www.symantec.com/business/support/index?page=content&id=TECH96924&locale=en_US
3) Cleanwipe tool - But need to contact support to receive this tool
https://www-secure.symantec.com/connect/forums/how-get-cleanwipe-tool
Best way is create a web case and support engineer will send you required credentials to download the tool.
How to create a new case in MySupport
http://www.symantec.com/docs/TECH58873
How to Create and Validate a SymAccount for using Symantec's MySupport
http://www.symantec.com/docs/HOWTO31127