You do not need to disable MSE to install other applications.
I have no idea what epp.msi is. How did you install MSE? Did you install fromwww.microsoft.com/security_essentials?
Did you uninstall AND CLEANUP, repeat CLEANUP, all other realtime antimalware before you installed MSE? If not, you must do so.
To disable MSE temporarily, open MSE, settings tab, select realtime protection, and uncheck "turn on realtime protection"
However, because you have tried uninstalling, who knows what is messed up now.
Perform these checks:
Verify that you have removed/uninstalled all other real-time antimalware products that were ever installed on your PC, including free/trial products that were installed when the PC was purchased (Norton, Symantec, McAfee,
TM, AVG, Avast, Avira, Malwarebytes (paid), etc).
Then, use the cleanup tools here: List of anti-malware program cleanup/uninstall tools If
yours is not listed, go to the manufacturer and get it.
Verify that your PC clock is correctly set (date, time, time zone). If not, correct it.
Verify that Windows Defender is uninstalled (if XP), or Disabled (if Vista/W7).
Verify that you are up-to-date with SERVICE PACKS and updates (including .NET and IE). Yes, it can take some time to do this.
Verify that the Windows Firewall is on, and set to defaults.
Verify that you are using version 2.0.657.0 of MSE (as of 2010-12-16).
Then, restart your PC.
You may need to remove and reinstall MSE as well. If so, you can use the procedure(s) here to uninstall MSE:
Uninstalling MSE.
Then, use IE or Firefox, and go to www.microsoft.com/security_essentials and click DOWNLOAD. Do not navigate and download via TOOLBARS.
If the problem persists, submit a support case to Microsoft: https://support.microsoftsecurityessentials.com/?scrx=1
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