Clean install of Win 7 Ultimate 64 Bit on to XPS1530 (using Vista Ultimate - 32 bit)

My first installation attempt failed and I could use some guidance regarding how to proceed.

After booting from the 64 bit disk, details of my HD are displayed.  Win 7 refuses to install on any of the Partitions for perfectly reasonable reasons.  I am not confident on how to proceed.  Here are the details...

Partition one is 78MB and 70MB are free.  The type is displayed as "OEM (reserved).  I presume this should remain untouched but I am not sure why.

Partition two is the "recovery" partition, has 10GB of which 4.3 GB is free.  It is characterized as "System".

Partition three is 173.7 GB and 173 GB is free.  It is characterized as the "primary".  This partition is protected by Bitlocker.  Win 7 install advises me to disable Bitlocker which seems perfectly reasonable.

Finally, partition 4 is 2.5 GB and only 567 MB is free.  It is characterized as "Media Direct".  Media direct never worked well for me and I ended up uninstalling the Media Direct software.

Command options within the Win 7 installation are (Delete), (Extend) - not sure what that is, (Format) and (New).

My general question is should all four partitions be maintained?  Alternatively, perhaps I should delete some or all.  It seems with a new OS the "OEM reserved" partition is no longer needed and perhaps the "Recovery" partition isn't needed either.  Maybe I should simply reformat but leave the media direct partition alone in case the Win 7 version is more reliable.

Any tips or suggestions are appreciated.