Boot drive setup with preexisting HDD

The simplest way to do this is to just install the OS again on the SSD and reconfigure everything. I'm assuming you mean Windows, so that would mean re-installing all your programs and copying over your documents, etc. There's an "Easy Transfer Wizard" that comes with Windows that's actually rather good for that purpose and it copies a lot of your settings too.

The hard way is to try to image your HDD and restore it to the SSD, but the partition tables will be all messed up. This would actually be easy to do if your HDD is smaller, but that's probably not the case so the above method is simpler. (If you do happen to have a 320GB or smaller HDD then you can use something like the G4L Linux distribution and put it on a bootable USB stick to copy over your HDD to the SSD.)

Unless you have multiple identical hard drives, don't worry about RAID - you want AHCI mode.

If you had two identical drives you can put them in RAID0 which writes half of everything to both drives. For example, if you had two 1TB drives you'd get 2TB out of it, and when you write 1GB to the array it would write 500MB to each drive. This improves performance - both read and write - but if either drive dies you lose everything since it needs the other half. With RAID1 it mirrors everything, so two 1TB drives becomes a 1TB array and if you write a 1GB file to the array it writes 1GB to each drive (2GB of writes total). This offers you redundancy, since either drive can die and you still have a copy of the data. With 3 or more drives, you can have RAID5 (RAID0 extends but becomes riskier with each additional drive). With RAID5, if you had three 1TB drives you'd get 2TB usable (with N 1TB drives, (N-1) TB). When you go and write 1GB to the array, it writes 1.5GB. What it will actually do is write 333MB of data to each drive and 167MB of parity to each drive. With RAID3 (not commonly available), it would write 500MB of data to drives 1 and 2, and 500MB of parity to drive 3. With RAID5, the parity is split across drives to improve performance. The parity is just a simple XOR (eg, 1 XOR 1 = 0, 1 XOR 0 = 0 XOR 1 = 1, 0 XOR 0 = 0).

Just for fun, imagine you wanted to write some bytes and they got spread out like RAID5. Let's say you wanted to write 0110 1011 (byte1), 1011 0001 (byte2). Then drive 1 gets byte1, drive 2 gets byte2 and drive 3 gets the XOR of the two. That would be 1101 1010. Now let's say drive 2 goes down so you have this:

byte 1: 0110 1011
parity: 1101 1010

If you take the XOR of that, you'll recover 1011 0001, which you'll see is byte2.

With 4 drives you can run RAID10, which is actually just RAID1+0, which is to say that it takes drives 1 and 2 and creates a RAID1 from them. Then creates a RAID1 from drives 3 and 4. Then creates a RAID0 from the two RAID1s. If any one drive dies, it's OK. If there's a second drive failure there's a 2/3 chance it's from the other RAID1 array so it's OK.