System Restore unable to complete due to missing .dll file?

What had occured was that my friend was watching a video on Facebook through her Facebook wall, and suddenly the computer decided to restart. Then she got a screen saying:

:(

A problem has occured with your PC and needs restart. We will recompile information about your error and soon it will restart. (63% Complete)

For more information, find out more about: BAD_POOL_HEADER

Then this occured:

System restore could not extract the archive (C:\Program Files\Microsoft Office 15\root\client\appvisvsubsystems32.dll) from the point of restoration. Error not specified during the execution of system restore. (0x80070017)

She has tried to click different restore points, and they all lead to the same error. She's also tried manually restarting the computer to no avail. What do I do to fix this?