Running Dell R710 or R5400 on Windows 7

I did this recently between two identical HP G5 servers without problems. Hardware-based RAID-controllers who arent stupid saves their logical volume configuration on the disks, so it should not be a problem if you have the same RAID controllers (at the same firmware version).

You should however make sure you have a very recent backup/ghost image of the logical volume before doing this.

It Depends. :) Your most likely useful scenarios will be to use the 2x146GB in RAID 1 pair for the system partition, but then either build two pairs with the other drives or build them all into one 1+0 array. A scenario where you'd put them all into one 4 drive array would include something like a file/storage server where you have random read/writes and want to maximize space capacity. A scenario where you might not want to do that could be an application or database server where you want to separate the code from the text logs (web server) or data files from transaction logs (database server) in order to increase performance by separating different types of traffic.