A few days ago I did a Super PI test on my old laptop with Windows XP and Windows Vista.

System:
- 1.5 GHz Intel Celeron M

- 512 MB RAM

Both systems were fresh installed with all needed drivers.


Results:

Windows Vista Windows XP
+ 000h 00m 02s [ 64K] + 000h 00m 01s [ 64K]
+ 000h 00m 04s [ 128K] + 000h 00m 04s [ 128K]
+ 000h 00m 09s [ 256K] + 000h 00m 09s [ 256K]
+ 000h 00m 24s [ 512K] + 000h 00m 23s [ 512K]
+ 000h 00m 58s [ 1M] + 000h 00m 57s [ 1M]
+ 000h 02m 24s [ 2M] + 000h 02m 21s [ 2M]
+ 000h 05m 23s [ 4M] + 000h 05m 17s [ 4M]
+ 000h 12m 18s [ 8M] + 000h 11m 54s [ 8M]
+ 000h 25m 42s [ 16M] + 000h 25m 52s [ 16M]
+ 000h 53m 33s [ 32M] + 000h 56m 07s [ 32M]

Conclusion: Windows XP did better with small calculations, but Vista beats it at larger calculations (16M and 32M).