multiple operating system but only boot's to one

[maximum10]

a m8 has suggested to try Ubuntu so ill give that a go cause i have no idea what else i can try 

[maximum10]

just had another look at the bios and the HDD's are set up like this

IDE Channel 0 master {none}
IDE Channel 1 slave {none}
IDE Channel 1 master {sony dvd rw]
IDE Channel 1 slave [hl-dt-st gce-8481b]
IDE Channel 2 master [WDC 74]
IDE Channel 3 master [maxtor]
IDE Channel 4 master [hitachi]
IDE Channel 5 master [none]

so looks like all my HDD are set to master, should i only have 1 master and the rest slaves?

[patio]

Just use the BIOS to switche between drives at bootup...
Does this machine have an addon PCI IDE controller card ? ?

[maximum10]

i dont think this machine has the option to change what order the HDD boot
its either HDD or floppy cd/dvd ect.

i dont if it has a PCI IDE controller card m8 

[maximum10]

ok so now i swaped my main HDD with the other HDD on my mobo
and when i boot up i get the NTLDR is missing.
would this be the reason i have no duel boot?