Hi RoseChristy, welcome to the HP Forums. HP Has tested your notebook (C7E03PA) to work properly with Windows 8.1 (HP & Windows 8.1) . I think the issue with the battery is simply coinciding with the upgrade, but not necessarily causing it. If the battery test reported a weak battery, you will most likely have to replace it. Here are some additional things to try however.
This document shows there is a firmware update which may help resolve a similar issue.
Battery Power Drains Faster Than Expected (Microsoft Windows 8)
Here is some further troubleshooting that might help, if the previous steps do not.
Battery Does not Power Notebook or Hold a Charge
Let me know the results.