Original sentence: If due care is not taken, this can often lead to thrashing.So the virtual address space might contain, say, twice as many addresses as main memory with the extra addresses mapped to hard disk space in the form of a swap file or page file
Edited sentence: However, if due care is not taken, this can often lead to thrashing.So the virtual address space might contain, say, twice as many addresses as main memory with the extra addresses mapped to hard disk space in the form of a swap file or page file (the default on Windows XP and later MS operating systems)