raid 0, definately - you can never have enough linear transfer bandwidth
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How exactly the SATA chipset is wired to the system bus determines the maximum speed you'll see, most onboard these days use a single PCI-E lane so you should be good up to 250MB/s - shouldn't be a bottleneck for 4 drives considering there are certain inefficiencies and overheads regardling rotational latency and command queuing each time you add a drive.
If you have a Intel chipset with matrix RAID, you can carve up the disks into logical volumes with different RAID types, eg, RAID0 for your game installs, swap file, temp files etc, and RAID 0+1/5 for your important data. (but remember even RAID 1 or 5 is no substitute for good backups - they just prolong failure, not eliminate it)
I get between 220-300MB/s depending on which benchmark I run on my disks, which makes a vast different in loading times over a single disk.
, 0+1 for fast speeds and system security 
, or choose any of the other available RAID functions? 
that must FLY iv got like 6 other harddisks for space and back up so thinkin RAID 0 out of 4 raptors for XP+vista install, and use seperate seagate drives to hold my information, will probably partition the 4drive array into 2 partitions, xp and vista
