just the bits, anything over 4gb ram needs to be 64bit,(because their is a block in 32bit operating systems) and that makes them not see any ram over 4gb most new machines are 64bit thats the way forward, but you may find certain softwares dont work or have problems, if you have 4gb ram on a 32bit machine, you may notice only 3.5gb, the other 512mb will go for video cards and the likes, This is just a classic mircosoft racing ahead and the software teams being behide, If you find it problematic for you, I would downgrade to 32bit untill more 64bit software is on the market
OK - quick update.....just transfering all the other items from one PC to the other....been going about 9hrs so far..
Uh..."You have been fined 99 bicycle clips, go directly to jail, do not collect 200 pounds... who's that naughty boy there?"