XP Create Network - No 3,5" Disk Drive

Greetings!
I have bought a new computer which like many these days has no 3,5" drive. I want to create a network with my other computers and need to make a network disk, but the new computer says it is not possible and this can be achieved only with a 3,5" drive.
I am surprised Windows doesn't give the option to use the CD drive in absence of 3,5" drive.
Please, can anybody tell me how I can get this option within XP network creation to recognise the CD drive instead of the 3,5" drive? Or must I buy an external 3,5" driver?
Thank you,
nippauls