i845 (non-G, non-E) *are* included in Win XP natively, so you don't need to worry. If you've got i845G or i845E, then you do need the chipset drivers.
I would personally also recommend using IAA (Intel Application Accelerator) which you can find
HERE as Intel's storage driver is better than Microsofts I tend to find. (On non-XP OS's, this also automatically enables DMA).
Hope this helps .