How can you get more than 4 IDE devices working at the same time?
I have DVD-ROM, CD-R, 2 HD
Next week I'm getting a 120GB HD, but I already have four - I don't want to take off my 30GB, after all, 30GB is still quite a bit of space...
Depends where you shop and what you want it to do; can be anything from £15 ($23) to about £200 ($300).
£15 will get you a standard ATA133 controller card that can support another 4 IDE devices.
£25 would get you the same card, but with RAID 0 + 1 functionality.
For around £50 you could get a higher quality RAID board; maybe supporting more disks or other RAID modes.
Lastly up to the £100s and you are looking at high-end workstation cards that will support 6 or 8 disks in most common RAID configurations.
I'm guessing you just want the £15 one though -- bear in mind the more drives you add the higher the load on your power supply. You can get stability problems if you load it too heavily; and disks take a lot more power than most of the other components.