Ok can someone please tell me what i should do, i have:

IDE Western Digital WD800 80gig
IDE IBM 120 GXP 80gig
IDE IBM 120 GXP 40gig
PCI Ultra ATA/100 Controller (not a raid card)

my problem is that i have so much stuff downloaded i dont want to keep backing everything up. e.g
backup 20gig of mp3's download more mp3's, then i have to backup my 20gig plus the new mp3's cos i dont have a good system of backing up files.

i have been told that raid 1 would be a good solution to this, because my hard drive would be mirrored i then wouldnt have to backup, which sounds good to me.

now i have 3 questions 1. does it affect the performance of the system, and if so by how much compared to a normal IDE hard drive. 2. what would happen if my motherboard fails, can i then just put one of the hard drives into another system and carry on as normal or do i have to put the controller card in and the other hard drive aswell. 3. will it work even though i have different hard drives, both run at 72000.

my plan also is to run my 40 gig as the main hard drive for XP and program files and have the 2 hard drives for my backups (mirrorred)

I assume you're planning on getting an ide raid controller card because the kind of software raid you can implement with XP doesn't include raid 1. Your two 80gig drives may work but it's a big maybe. They need to be identical physically.

The performance of RAID 1 (assuming it's hardware-controller based) is comparable to that of a single drive. Writes are a little slower but reads are a little faster, so it balances out.

RAID is not really meant to be a substitute for a data backup system. The only real purpose of RAID 1 is to reduce downtime when a system fails due to a hard drive failure. Servers running RAID never rely on RAID as their backup program. There are a lot of reasons for this. An obvious one is that if your data somehow gets hosed on your main drive (for example, due to a virus) it will instantly get hosed on your mirror.

There are cheap backup solutions that will perform this data mirroring operation without RAID. One is Iomega's Quiksync. Let's say you have two data folders, DATA1 located on Harddrive1 and DATA2 (your backup destination) located on Harddrive2. You can set up this program to automatically synchronize these two folders. You download an MP3 to DATA1 it will be immediately copied over to DATA2. You don't have to do anything. The first backup or synchronization will take a long time because it's copying over 20+ gigs of data to the backup folder (DATA2). But from then on it will only copy files that are new or have changed (overwriting the older version). Quiksync runs about $40 from Iomega's website. Note that the Quiksync that comes bundled with Iomega drives won't work because this limited version will only work with Iomega drives, like zips or jazz drives, but the $40 version will work with any mass storage device including networked drives. I've found this program on Ebay before for less than $15.

The only thing I'm not absolutely certain about is when you open an MP3, whether Quiksync would then think the file had changed and then overwrite the "older" version on the backup drive. I doubt it very much. The nice thing about this program aside from its syncing ability is that it doesn't change the format of a file into an archive data type, and so doesn't require any restoration procedure like backup exec or msbackup/ntbackup.

Ok yeah i didnt think what would happen if i were to get a virus, so raid 1 and quicksiync are out of the question. I think i will have to buy a DVD writer, which is annoying because there is no set standards at the moment and probably when i buy mine it will be of no use in about a year, because it will be replaced by another DVD standard. anyone know what i should do? does anyone have any good suggestions on which DVD writer to buy?
Thanks

Quiksync doesn't really pose the same problem as mirroring, especially if you're mainly backing up MP3s, which aren't likely to be infected with viruses. When you backup using a program like Quiksync you're only backing up a single or few directories of your entire system, so while it's possible you could end up backing up a virus, that's true of any kind of backup, including DVD-R. You can avoid this hazard by using a virus scanner, which you should use anyway even if you're backing up to DVD-R. If you already find backing up inconvenient, wait till you buy a DVD-R for 20-30gigs of data. They are slow as hell and will be a pain because you can't automate or schedule backups. Makes a lot more sense to back up to a second hard drive using a backup program like quiksync. This is much faster and can be automated.