Your driver maight not work completely if you fail to install it according to order, this method order is the best i ca find, the most important things is when installing driver the chipset come first and the either AUdio or graphic.
Based completely on HP available softpaqs:
1. NX9420 BIOS vF.1a (plus CMOS "Set Defaults")
2. Seagate HD Firmware v1.00a (if applicable)
(Install Windows XP)
3. Intel Chipset Support 22.214.171.1246a
4. ATI or Nvidia, depending on what you have
5. ADi SoundMAX v5.10.01.4321
6. Microsoft UAA Bus Driver v1.00 A6
(might need to swap order of #5 and #6)
7. Broadcom GbE NIC v126.96.36.199
8. Conexant or Agere Modem Driver, depending on what you have
9. HDA Modem Installer v1.00 B
(might need to swap order of #8 and #9)
10. Intel or Broadcom Wireless NIC, depending on what you have
11 HP Integrated Bluetooth v4.00G
12. HP Wireless Assistant v2.00E
13. TI Media Card Driver v188.8.131.52a
14. High-speed SD Card Driver v184.108.40.206a (read Release Notes first!)
15. HP Mobile Data Protection System
16. Authentec Fingerprint Driver v1.00D (if applicable)
17. HP ProtecTools Security Manager v2.00D
18. HP Credentials & FP Manager for PT v2.00D
19. HP Embedded Security & TPM Driver v4.50a
20. HP Bios Configuration for PT v2.00c
21. HP Device Access Manager for PT v2.00a
22. HP SmartCard Module for PT v5.00d (if SCM is installed)
23. JavaCard Security for PT v1.00B (if using JavaCard)
The following are the "optional" items (no particular order):
* HP Battery Check v1.00a
* Synaptics Touchpad Driver v9.1.11Q
* Help and Support Center v4.4C
* HP Accessories Product Tour v13.00
* WinDVD Player
* LightScribe Host Software 220.127.116.11 N (if using a LightScribe drive)
I'm not aware of any "requirement" to install QuickLaunch 6.00 before 6.30 nor is there any mention of it as a prerequisite in the release notes.
Taking this a step further, I would install the "latest" versions of the following instead of the ones available on HP's website:
3. Intel Chipset Support v18.104.22.1680 from Intel's website
4. Latest WHQL driver from either ATI or Nvidia website
7. Latest Broadcom B57xx driver from Broadcom's website
(plus BACS utility found under "NetXtreme II"
10. Latest Intel Pro/Wireless NIC driver and client from Intel Website.
After all this, Windows Updates.
Again, I've never worked on an NX9420, but this is how I'd approach it.