I didn't know you could slipstream windows7, remember reading something about microsoft trying to prevent people from doing it ages ago.
Might have a look
could do a minimal style install on my laptop as the spec is like a netbook
altho linux runs fine on it.
I never really customised the install of vista/xp before tho just used nlite to slipstream the service packs and updates so I didn't need to download them again.