Data in Virtual Memory?

Virtual memory is discarded at reboot, but it is not zeroed -- that is, someone could use a recovery program to scan unallocated sectors and potentially recover what was written. VM is first in first out but there is no way to be 100% certain it used the same drive sectors, so the likelihood is that it was overwritten by further use but not certain. There are also other temporary files that software programs create which are deleted but not zeroed. So there is no way to guarantee you that the confidential material is not recoverable. It is not likely, but it is not impossible.