[Samba] Large Files vs. Speed

[Patrick blitz]

Hey Lists.

i'm pretty sure my Problem is pretty common, so please point me to the FM, if there is any (i couldn't find it searching the list archives and  google)
here's the deal:

i've a Linux Box as a Server for a small VideoEditing 3D Company. The Server and Workstations are connected over 1GBit Ethernet. The Linuxserver runs Suse (9.2 if i'm not mistaken). The Shares in question are on two IDE Disks.

Problem:
The overall Speed of the System, esp. under a bit more Load, is way below the Windows System that was on the box before. 
Writting Two Files with about 300 MB each takes up to 2 Minutes each (which is just too long for 1Gbit). 

I know that a big part of this are using IDE - Disks, but still, why would WinXP be faster writting those than Linux?

Any turns i could turn to make samba a bit faster saving the files?

All Parameters in smb.conf are in Default.

Thanks a bunch,

Patrick