Single core is a lot worse than I remembered. I had booted up my wife's college desktop with a P4 in it. Pretty unusable experience, I eventually gave up on trying to reinstall Windows before giving it away.

Pentium 4's pretty bad by modern standards, unfortunately. It's well over a decade old and wasn't all that great even when it was introduced. I think the cut-off for "good enough to be used today" is somewhere around the Core 2 Duo which was introduced a decade ago and was a huge step up from the Pentium 4.