first of all, no IDE drive ever really has the constant throughput of what it is rated (ATA/133, 100, 66, 33). ATA/133 has no real performance gain over ATA/100. They only ever run at 50 to 60 MB/sec on a very good day, and will rarely even peak at their 133MB/sec or 100MB/sec rated speed. That said, SATA 150 will run noticably faster than any IDE drive, i have seen reviews where one SATA 150 drive matches the speed of a RAID level 0 configuration of ATA/100 drives. This is because it runs a dedicated line to each drive, so there is no 'master' or 'slave,' just a drive, a very small cable, and the connector on a SATA controller or SATA equipped motherboard, no jumpers, no 80pin ribbon cable. The benchmarks of SATA drives are considerably faster than most IDE drives, and the peak speed is much higher. but you need more than just the drive...you need a SATA cable, a SATA equipped mobo or pci controller, and (depending on the drive) a SATA power adapter.
If you are just looking for startup times, it is simply not worth the upgrade. If you want overall added performance, go with SATA. If you are comfortable with the size of your current boot drive (40GB), go with the raptor. it is 37.6 GB, 10000 RPM (HUGE performance gain), and the only drive that can really take advantage of what SATA has to offer. If you just want an 80GB SATA drive, get the WD that you mentioned before.
As for RAID 0 (striping), you need two like drives and a raid contoller. Promise makes very good controllers if you do not already have one built into your mobo. SATA in RAID 0 is VERY fast, and you will definitely notice a speedup in boot times for XP as well as every other area of performance. Problem is, if one drive crashes, you lose the combined data on the two of them.
if you really are serious about getting a performance boost, and not just faster boot up times, get SATA, if you want faster boot up times, there are some apps out there (I even think there is one in the MS PowerToys package) that will load xp into the ram when booting and expedite startup. once started, it will unload xp back to the hd. I think it is called tweakui.