I'm using Explorer 8642HD. It started to reboot by itself multiple times today. It showed HdEr where it supposed to showed the time.
After checking other posts, I think the Hard drive failed. For the time being, can I stop the PVR from rebooting, almost every hour?
You may want to check to see if the signal to the 8642 is OK. See the following post on that topic:
If the rebooting continues after confirming that the signal is OK, then you may wish to disconnect the iHDD, or replace it. Here's a thread on that topic:
It may not be worth spending anything on the 8642 since it's so slow, so you could either consider getting a used 9865, or switching to IgniteTV.
Here's a thread listing all the things to be aware of if purchasing used.