Here is what the TI Knowledge Base has to say about resolving the problem you have.Hope it helps.How do I resolve the error "Access Denied" when transferring an App or OS using the TI Connect software?
The error "Access Denied" indicates that the TI-Connect
software could not complete the current transfer due to an unforeseen
error. Please try the following troubleshooting steps if the error
persists.Perform a manual "Garbage Collect" on the calculator (TI-83 Plus and TI-84 Plus family only):
• Press [2nd]  [TAN] [ENTER] [ENTER] .
NOTE: A manual "Garbage Collect" can take up to 5 minutes to complete.
• Attempt to transfer data to the calculator.Uninstall and reinstall the TI-Connect software:
• Go to Start >> Settings >> Control Panel or Start >> Control Panel and select "Add or Remove Programs".
• Locate the TI-Connect software in the list and then choose "Remove".
• Once the software uninstall process has completed, please shut down and power off the computer.
• Wait approximately 20-30 seconds and then reboot into Windows.
• Download and install the latest version of the TI Connect software from the TI Connect Software home page.
• Once the TI Connect software install process has completed, restart the computer before using TI-Connect.
• Attempt to transfer data to the calculator.
If the above troubleshooting steps do not work, please contact TI-Cares Technical Support
for additional troubleshooting.