I cannot tell, from here, whether the keys you wish to pass are correct: that will be an issue of trial and error.
But I can tell you where you are going wrong: You need to add those keys to the APPEND line to pass them directly to the kernel.
For the last example you posted, this would result in a isolinux .cfg like this:
DEFAULT default
PROMPT 1
TIMEOUT 26
DISPLAY boot.msg
LABEL default
KERNEL kernel
APPEND vga=normal devfs=nomount pxe ramdisk_size=55000 load_ramdisk=1 init=/linuxrc prompt_ramdisk=0 initrd=initrd.gz root=/dev/ram0 rw noapic nolapic lba combined_mode=libata ide0=noprobe nomce pci=nomsi irqpoll quiet Server=192.168.x.x Share=Partimage$ User=domain\SRV_Partimage Password=pword Directory=GX620 After_Completion=Reboot Replace_BIOS=Y CIFS_Preferred=Y No_Shell=Y AUTO=Y
Notes:
- As I said, the values of the keys have to be tested, this is only giving you the way they have to be passed.
- Don't forget Linux is case-sensitive!
- Two keys that I'd expect to be problematic:
--- Share=Partimage$ ..... Try without '$'
--- Directory=GX620 ....... Try "\GX620", "/GX620" and "\\192.168.2.40\GX620"
