james221 wrote:I was replacing it with a string of the same length.
A string of the same length is not necessarily of the same data. Length doesn't matter, the CRC result matters. Just try changing a single character in a string, then compare a new CRC with a CRC before the change:
The quick brown fox
jumps over the lazy dog. < CRC32:
519025E9
The quick brown fox
Jumps over the lazy dog. < CRC32:
AF46DB93
The single capitalized "J" kils the CRC.
You need to make a new CRC after the edit and shoehorn that result in place of the old result too.
This is all theoretical, untried by me. I do not know the CRC type used by Virtualbox. Expect unusable results, make backup copies if the data is important.