I sorta have similar dingy with you.
Just couple of days ago I wanted to install ZenMini on this PC#3 with no cd/dvd drive. What I did was insert a 4GB thumbdrive on PC#1, bootup to ZenMini cd and install to 4GB thumbdrive (it auto-install this as EXT4). Rebooted and boot up ZenMini via 4GB thumbdrive (works).
Next.. I moved the 4GB thumbdrive to PC#3 and tried booting it - I only encounter a tiny problem ( this one got ATI 3400HD, the other one got Nvidia GTX260). It auto-fix the video driver by just me hitting <enter> few times... and few seconds later.. I'm IN !
It auto-detected everything (the harddrive partitions on this PC#3, the network card on this PC, etc)
Then just last night.. I used GHOST4Linux (bootable cd) to clone the usb 4GB thumbdrive (ext4) to this PC's 40GB pata drive
Maybe you can try the same !