What's the max size copyable with CopyMemory API call?

I know that the referenc hpvDest and hpvSource can be defined as like:
Byval hpvDest as Long
so that I can use them in conjunction with varptr to work with memory locations directly (which then allows for adding and subtracting memory locations to move stuff in memory like an array), however I doubt that even though it is using a long (a SignedInt32) that it could actually transfer &h7FFFFFFF bytes at once. In fact it crashes when I try to copy merely 100000 (&H186A0) bytes at once. What is going on. Is it really incapable of transfering large ammounts of data at once? Will I need some kind of for-next loop to transfer several megabytes of data?

I think the crash is more likely caused by trying to write to somewhere you are not supposed to.

How about showing us an example of the code that is crashing. Also include the declare you are using for RtlMoveMemory as there are a few subtle variations.

Edit: in answer to your question I believe the copy size is limited by the available contiguous memory and the size parameter which is defined as an unsigned integer of 32 bits.