Hi Stephen,
Thank you for posting your query on Microsoft Community.
As per the issue description you are unable to access a shared file/folder from another computer and troubleshooter reports that Peer Name Resolution service was not running.
If it is not running try to follow the steps provided below to start that service and see if it helps you to start it and fix the issue.
Step 1
Temporarily disable security software.
Follow the steps in the article below to temporarily disable security software.
Disable Anti-virus software
http://windows.microsoft.com/en-US/windows7/Disable-antivirus-software
Note*: Antivirus software can help protect your computer against viruses and other security threats. In most cases, you shouldn't disable your antivirus software. If you have to temporarily disable it to install other software, you should re-enable it as soon as you're done. If you're connected to the Internet or a network while your antivirus software is disabled, your computer is vulnerable to attacks*.
Step 2
Now try to start the service by following the steps provided below.
Press Windows key + R
Type services.msc in the run box.
Scroll down and search for Peer Name Resolution service.
Right click on this service.
Click on Properties.
Try to start the service and make sure that start type is Automatic.
Additional Information:
You may also refer to the article mentioned below.
Error 997. Overlapped I/O operation is in progress: KB2918614 breaks Windows Installer Service
Hope this would help. If issue still persists post back with the information required, current status of your computer and result of the proposed suggestion, we will be happy to assist you.
Regards,