We've currently got Trend Micro as our anti-virus, but will be switching to Symantec Endpoint Protection (SEP). (This is for Windows XP and Windows 7 machines.) My co-worker removed Trend Micro, but couldn't install SEP, because it wasn't able to access the Internet. She suspects that removing Trend Micro resulted in her not being able to access the Internet. If that is the case, then what do we do about it?
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Sounds like your co-worker didn't follow the proper instructions for removing TM. The first step would be to use a system restore point to put TM back. Next she will need to use the Trend Micro Diagnostic Toolkit to uninstall TM(the 32 bit version is here).
After that, do the following:
I hope this helps