combine two internal hard drives into one

[DDRmaster554]

Not literally, but if I have two internal hard drives (both separate from the main one) can I have them be stored under one drive letter? ie. have 3 hard drives, one C: for the local disk, and the other two under E: for backups, extra storage, etc...

[MaDef]

Yes you can if they are sata drives. If they are ide and you have xp pro, you can convert the disks from basic to dynamic. your motherboard has built in Raid support. You'll need to set the raid option in the bios, you'll then need to assign the 2 drives to an array. (check your motherboard manual for detailed instructions).

You may need to reinstall the operating system I'm not sure if you can add a raid array to windows after it's installed (I've always installed the raid drivers during installation).

Remember to back up any data you wish to keep, since you will loose all data on the disks you are converting.

[Kuusje684]

Like MaDef said - RAID is the key here. More info about it can be found here. You can merge 2 discs into 1, no more.

You'll have to make sure what you're going for because you sadly can't 'just' change a RAID setting (read the wiki page to find out why). If you want to merge 2 discs to gain speed (but no extra backup of any kind) then you'll want RAID 0. Keep in mind that with a RAID0 setting 1 busted hard disc will kind of drag the other HD with it because the data is split over 2 drives. You'll have faster reading/writing speed but each disc has 50% of the data so a RAID0 disc on it's own is useless. The lost data (in case of drive failure) on the other RAID0 disc will be lost and can not be recovered, no matter what. This may sound rash but keep in mind that with no RAID settings at all and a busted HD you're screwed as well, tho you can recover data from it if it fails.
1 more advantage of RAID 0 is with copying bigger files. Copying/cutting & pasting big files can take a while with big files if you move 'm from 1 driveletter to another. With RAID0 2 drives will have 1 driveletter, thus eliminating the 'copy/paste time'.

If you do want a backup of 1 disc, RAID1 will be your choice.
Keep in mind that a RAID1 backup is made with hardware failure in mind. If 1 breaks you can use the other (the data on them will be exactly the same all the time). Data loss due to accidental delete etc will accour on both discs, thus not providing a backup.

Seperate HDs (external or not) are the best way to keep data secure in my opinion. If you need more info feel free to ask .

Edit: if you want to set 2 discs into RAID, they have to be the same size. For example: setting two discs of 200 GB into RAID will result into having one 400GB drive with 1 driveletter. Put a 200GB and a 250GB disc into RAID will result in a 400GB RAID disc (2 times the SMALLEST disc, the 50GB of the bigger drive is unasignable (correct me if I'm wrong about that!)).

[l337_GuY]

I would suggest just using JBOD (Just a bunch of disks). It works with ANY size and just adds all the HDD's together into 1 drive.

With RAID0, You should atleast match size. But if you want to see any gain in performance, same brand and model number drives are better. If you don't have the same drives, I wouldn't recommend RAID0.