I guess, this is due to improper install/uninstallation. It seems that some of the files still exist even after uninstallation. The best way to clean this up is to
1. Go to control Start->Settings->Control Panel-> Add remove programs . Remove both the Cisco IP Softphone and the Cisco TSP applications one after another.
2 .Delete the folder for Softphone from C:\Program Files\Cisco IP Softphone
3. Also delete the folder containing uninstall information by finding only the files related to softphone from C:\Program Files\InstallShield Installation Information
check for the entry "Appname=CiscoIPSoftphone" in the setup.ini file .
4.Remove registry entry for Softphone
5.Restart the PC
6.Re-install the SoftPhone.
This should help.