RAID setup

What would be an ideal RAID set up if my primary concern is speed and then redundancy?

CPU: P4 3.06GHz
RAM: 2GB RAMBUS
RAID card: Adaptec ATA RAID 2400A w/4 IDE Channels
HD: 4 WD 120GB 7200RPM 8MB Buffer and can add one more
OS: XP Pro
Primary software: Video editing

1). RAID 0+1?
2). RAID 5?
3). OS in HD1 and RAID 5 on other HDs?
4). Pros and cons?
5). any other ideas?

A brief set up procedure will be appreciated.