Just make sure the inside of the case and fan blades are clean.

The fact that it even run without the +4 plug is a surprise. But it should be OK, but keep a eye on it for a couple days.

If it acts up a bit, run chkdsk /f /r
that should straighten things out. But if XP was installed 3 or more years ago, I would do a clean install. Fact is this rig is starting to act up after 3 years since install.