Question: My laptop is Lenovo T400, whose CPU is 64-bit and RAM is 1x2GB. When I bought it, it already had 32-bit Windows 7. Then I partition the hard drive and install 32-bit Ubuntu 12.04 alongside Windows 7. 

Now I am going to reintall the Ubuntu part from 32-bit 12.04 to 64-bit (possibly the latest version), while still keeping 32-bit Windows 7.

I am also going to change my RAM from 1x2GB to 2x4GB.

1. I heard that I have to make some change in BIOS (from a commend on
my another post, which has now been deleted). Do you know what
change it is? Is it for reinstalation of Ubuntu from 32-bit to
64-bit, or for changing RAM from 1x2GB to 2x4GB?
2. What is the order of the following steps: change BIOS, reinstall
Ubuntu from 32-bit to 64-bit, change RAM from 1x2GB to 2x4GB?

Thanks!

Answer: 
No steps required really. I would load the system with the memory and then go ahead with the Ubuntu install. Keep in mind that Win 7 and Ubuntu 32 bit will load quite happily with 8 gigs of memory but at the most will only be able to access 4 gigs tops.

Consider upgrading your Win 7 to a 64 bit version too - just sounds like a waste to have a 32 bit OS on an 8 gig system.
No Bios changes required. simply goahead. probably this is the interface you're going to work with

![enter image description here](https://i.stack.imgur.com/uUZEl.png)

Just Customize the existing ubuntu partition(meaning just delete and create again)

then just press next, next, next and you're there. you don't need to worry about bootloaders ubuntu GRUB will Take care of that. by the time you boot that will show you GRUB. hope you're familiar with that. in case any problem with boot order or GRUB just install EasyBCD <http://neosmart.net/EasyBCD/>

this allows you to Edit the boot order and more other things as well