Could someone explain what this means? (Intel Syntax, x86, Windows)
and dword ptr [ebp-4], 0
The dword ptr part is called a size directive. This page explains them, but it wasn't possible to direct-link to the correct section.
Basically, it means "the size of the target operand is 32 bits", so this will bitwise-AND the 32-bit value at the address computed by taking the contents of the ebp register and subtracting four with 0.