Technically yes, but it's not a good idea. Many programs expect to have
virtual memory available even if it's not used.
Not really. A benchmarking program might show a difference, but
real-world performance will feel the same. The only time it makes a
noticeable difference is if Windows increases the size of the swapfile
and starts some disk thrashing which will slow things down.
You can set a fixed swapfile (virtual memory) size so Windows doesn't
have to resize it, and that will produce similar results to disabling
it. Something in the range of 512-1024 megs should be fine for many
users, depending on your usage of course.