If you just have a standard Win7 installation then the Ubuntu CD will
guide you through the creation of a dual boot and will automatically
re-size the C: drive to create space for Ubuntu - usually splits the
free space in half but you can adjust this if you want to, or just
leave it at that. The automatic process will also create the swap file
at an appropriate size so no need to worry about that either :-)

There are two basic ways of creating a dual-boot - running the Ubuntu
CD at boot time ( i.e. not going into Windows first ) will physically
split the C: partition and give the fastest performance. If you start
Windows first then put the Ubuntu CD in and create the dual-boot that
way ( the WUBI installer ) then this creates a large file in Windows
that is used to install Ubuntu into. The advantage here is that it's
easier to remove later but does have a performance hit.

Having said that, Win7 has much better partition handling and if you
did physically partition then wanted to remove Ubuntu then that's not
too difficult as the Ubuntu partitions can be deleted then the C:
drive expanded to reclaim the free space using Win7's Disk Manager.

Whichever way you go, you can let the automatic setup do its stuff :-)

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