so i've built myself a computer once, but it has a single HD with a single SATA150 connection. I've never set up a raid array or anything like that. now i'm looking to build my girlfriend a computer and she's on a budget, so we're looking at last-gen cpus and mobos, which means i'm not seein much in the way of SATA connections on the mobos. so could someone explain to me what PATA is? is it multiple HDs? and if so, would i have to have 2 OSs installed, or could i get windows to see it as one big one, or would i just have like, a C: drive and an E: drive or something?

PATA is the current hard drive interface that you are familiar with. It has the wide 40/80 wire cable. SATA is the new interface that uses a small cable. They use different controllers. Raid is a separate thing that allows you to combine hard drives. It's available for both PATA and SATA.

You don't have to have an operating system on every drive. Windows would be on C: and then the other one would be E: ect.. One use for RAID can be to make multiple drives seem like 'one big one'. If your on a budget I would forget about RAID. Get one drive, the largest you can afford.

Besides which, if you want redundancy....you'ld require a RAID 1 or 5 array. Anyone installing an operating system on a RAID 0 needs to have their heads examined if they're not doing comprehensive backups daily as RAID 0 has no redundancy. A RAID 1 requires two drives and you only get the total of 1 drive to use as the other is a copy of the 1st and is there to take over should the first drive fail. A RAID 5 requires 3 drives minimum and you only get the total storage of 2 of the drives (assuming in both cases you're using identical size drives). For a low end system (ie: home user) you don't need RAID at all. I know a lot of people are installing OS's on RAID 0's these days because they've heard you get better performance and speed. Well, while you might gain some performance and speed....the possible problems (like having one of your drives crash and losing all data on both drives) makes it not worthwhile to go that route.

PATA is also known as ATA or IDE. Intel P4 3.2E Ghz@ 3.8Ghz Asus P4P800-E Deluxe Kingston 2x512MB PC3200 D-Channel Asus AX800 Pro WD Caviar 160 GB WD Raptor 37 GB Zalman Reserator 1

I personally have my OS on a 2 disk RAID0 array. While the chance of a HDD going down is theoretically doubled, hardware failures are very rare. The perceptible performance increase is certainly not double because of other factors (eg. seek times) but it depends what your doing. Long linear read/writes give the best performance increase. You should always keep backups of crucial documents anyway. If my PC goes down I have access to friends and University PCs. If I have to re-install the OS its a pain but not life or death for me. Everyones situation is different.