To do RAID 0 + 1, you need four individual hard drives (they should ideally be the same exact model and size). The RAID0 part takes your data and puts half of your data on each of the first two drives, so it can be retrieved twice as fast (in theory). The RAID1 part uses the third and fourth drives to make a spare copy of the first and second drives, in case one of them fails. Without the RAID1, you would lose all of your data if one of the RAID0 drives failed.
So with your five drives, you could use the big one as your boot drive and put your programs and data on the other four after making a RAID10 out of them. Keep in mind that many of the IDE RAID controllers built into today's motherboards can do RAID0 or RAID1, but not RAID10... you'd need to buy a separate PCI RAID adapter, and because the IDE RAID adapters work best with just one drive per channel, you would need a 4-channel adapter with four cables. Guess what, this is getting a bit expensive for the moderate boost in sustained speed. Do you really need RAID? If you just need fast access to a relatively small amount of data, then get an Ultra160 SCSI card and a 15000rpm Seagate Cheetah X15-36LP. With a 3.6ms seek time and sustained throughput in the ~60Mb/sec area, it'll give very good performance (and has a 5-year warranty and runs pretty quietly too).