can someone tell me why my old generic pc starts and runs about 10 times faster than a dell 2400 series?

Question

my old generic runs windows 200 pro, and the dell runs windows xp.

Answer 1

You've answered your own question

Win2000 it simply a facelift on WinNT, a fairly reliable, and efficient OS.

WinXP has so many extra bolt on, make it look good and slow it down accessories.
So many "additional things" to load it needs more time to load.
You can speed up XP too by disabling loads of stuff on startup . . . if W2K loaded all the stuff XP had to on your old PC, it WOULD take longer to load.

Answer 2

For the same reason that my old computer with Windows 95 is faster than my newer one with Windows XP.