Cant burn faster than 2x on a Sony DVD Burner

Hi, I have a Sony dvd burner and when I use Nero or CopyToDVD I cant burn at 4x no matter what media I use.

I decided to try the “nero speed test” before burning and to my horror the fastest that the dvd files on my 7200 rpm hard disk will read at is 2x thus I am only able to burn at 2x even with 4x media.

I have the latest firmware for my writer so I was wondering what the heck is slowing my read speed of my HD to 2x as ive tried burning from both NTFS and FAT32 partitions with the same results.

I am using 4x Ritek die silver unbranded discs and 4x Princo die with the same results and the latest version of Nero (5.5.10.20).
DMA is defo enabled and working so Im stumped at this problem as it appears as if my HD is at fault but I have now tried burning from 3 different HDs with the same results

Can anyone help me please?

P.S. My PC spec is below so you have an idea of what my hardware is.

Mobo: Gigabyte GA7VRXP Rev 1.0 with modded F9 BIOS CPU: AMD Athlon 1.8 Tbred @ 1725Mhz, 150 FSB, 1.71v VCore
CPU Cooling: Zalman Flower {42°C Idle, 50°C Load} Memory: 2 x 512MB PC2100 DDR
Graphics: NVidia GForce 2 MX400 64MB Storage: 1 x 60GB Maxtor, 1 x 120GB Samsung, 1 x 80GB WD
DVD: Sony DVDROM & Sony DW-U10A CDRW: Plextor 24x Burnproof
Monitor: Compaq MV740 17" @ 1280x1024 Sounds: Cambridge Soundworks FPS 2000 Digital Speakers
Input: MS Wireless IntelliMouse Explorer, Logitech Wireless Keyboard Net: 1MB Fat Pipe, USR8000a NAT Router

Excuse if this is a stupid reply but are you using RW or R media. If it’s RW currently you will only be able to burn at 2X max – you will probably find running Nero or some other tests your burn rate is actually about 1.85X
If it’s DVD-R you should be able to burn at 4X provided you have 4X media AND the hardware device (i.e your burner) supports it.
If you are using proper DVD-R 4X media and your device is rated at 4X for burning DVD’s the only thing I can siggest is that you see if there is a firmware upgrade required.

(I’m using 'Doze XP as a guest running vmware on Linux Mandrake 9.1 and 4X works on LG burner – can’t tell if Mac supports 4X or not).

There is a firmware bug in the Sony which sometimes inhibits Ritek G04 @ 4x.