That is a really open ended question as there are many options available to you.
One option if you like Pinnacle is to move up to Liquid Edition. Check out Pinnacle's site and they have the upgrade pricing and all the information.
Another option which is highly rated here on this board is the Adobe Premier Pro or maybe Premier Elements but not sure if Elements allows you multiple video tracks.
Sorry, I personally do not have either nor used them yet but looking at upgrade one day in the near future for multiple tracks as well.
AMD Athlon 3200
Asus A7N8X Dlux
1 Gig Mem
Windows XP Pro
2 Seagate ATA 160 Gig HD,1 Maxtor 120 Gig HD
Sony DRU-510 DVD/CD Burner
Pinnacle 10 PlusMediaSuite
PremierPro 1.5 Suite
Sony HVR-A1U 1080i HDV Camcorder