Initial Problem:
During installing TekService user got the error message: "Installer has encountered an unexpected error installing this package. This may indicate a problem with this package. The error code is 2869." User was unable to complete the installation.
Troubleshooting process:
As far as the error message indicates the possible problem with the package user downloaded the latest package. The package was tested on testing PC by the expert. However user got the same error.
The next step was checking the Add/Remove programs list for old TekService installation. TekService wasn't in the list of installed programs.
After several other troubleshooting steps we noticed that TekService service is still present in Services list. That was the reason of installation failure.
The reason why TekService service was still available was uninstalling program with third-party uninstallation software instead of using Add/Remove programs applet.
Solution:
Solution consists of manual deleting TekService service and restarting PC.
The following steps describe how to manually delete service:
1. Press Start and choose Run.
2. In the Run window type "regedit" without quotation marks and press Enter. Registry editor should open.

3. In Registry Editor navigate to HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Services key and locate TekService key.

4. Delete whole TekService key with all subkeys.

Confirm the action by pressing YES.
After deleting service and rebooting PC user was able to install TekService.