4-pin molex to SATA power adapter? Yep. Works just fine.
Since HD makers know that the adapters are in common use today, they don't require the 3.3V line that is present in the standard SATA power connectors (without the adapter). If you want more info on this Google: SATA 3.3V power
SATA HDs work just fine in systems with other PATA HDs present.
Download and install the latest SATA driver for your motherboard.
If your motherboard can handle only SATA 1.5Gbps (not 3Gbps), then jumper the SATA drive accordingly.
Enable SATA HD detection in the system BIOS (usually set to "automatic").
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Note that if you install of XP to the SATA drive, you need to provide the SATA/RAID driver to the XP installation program (the F6 procedure). The XP CD doesn't have an SATA driver.
Hey, I'll put the basic questions first and then you can read the boring extras if you want.
Motherboard: P4P800 SE (2 X UltraDMA 100/66/33 and 2 X Serial ATA)
Power Supply: Doesn't have Serial ATA power connectors
Current HD: 80 gig WD (using one of the UltraDMA slots)
I want to upgrade to a Seagate Barracuda 7200RPM 16MB Cache 320GB Hard Drive. Will this hard drive work with an adapter from the four pin power cord to the serial ATA power cord? I heard that some required a 3.3 volt input or something like that. Will I be able to use both my serial Seagate hard drive and the UltraDMA WD hard drive simultaneously? This is important to me as it will make transferring data much easier.
Don't have to read this part:
I know my system can't take advantage of this hard drive. I am trying to get a hard drive of this quality or higher to work with my system so that when I upgrade the rest of the system later I won't have to upgrade the hard drive at the same time. The rest of the upgrade isn't going to happen till the major bugs have been discovered and worked out of Vista though. Until then my current hardware except for the hard drive is good enough for what I do.