Hi...
Step 1:first uninstall previous version of symantec
Step 2:download the new package from symantec site.Note download it in fresh system.
Step 3:copy that in pen drive. install the package immediately.
Step 4:If same problem occurs format the pendrive then copy and install it quickly.
step 5:if error occurs again do it step 4 again.
Step 6: i hope this will works fine.