I have my Xbox set up as a Media Center extender and the backward skip interval of only 7 seconds was too short. The extender skip interval can be changed, but has to be set via a registry change on the PC serving the extender. Steps:

• Turn off the extender.
• Log into the PC hosting the extender
• Open Control Panel – Folder Options and uncheck “Hide protected OS files”
• Locate the user account name that the extender logs in with. Look for a folder located in c:\Users with the format: Mcx[Number]-[MachineName]
• Run regedit.exe, highlight HKEY_USERS, and click File – Load Hive. Browse to the user account and select NTUSER.DAT
• Give the hive a key name, such as the extender user name you found earlier
• Under HKEY_USERS, expand your newly added key and navigate to: Software/Microsoft/Windows/CurrentVersion/Media Center/Settings/Video Settings
• Set a decimal value of 12000 on InstantReplayInterval to set a 12 second skip back. SkipAheadInterval determines the skip ahead amount.
• Highlight HKEY_USERS and go to File – Unload Hive. Fire up your extender and verify the new intervals.

Having problems? Post below and I’ll try to help you out.