Is my Ubuntu install 32 or 64-bit?

Go into the terminal and type in.

uname -a

If your results are similar to the one below, then yours is 64-bit; otherwise, it is 32-bit.

Linux ubuntu-tm 2.6.35-28-generic #49-Ubuntu SMP Tue Mar 1 14:39:03 UTC 2011 x86_64 GNU/Linux

If you have the x86_64 then your machine is 64-bit.

If your results are similar to this one; then you have 32-bit.

Linux Server 2.6.15-23-386 #1 SMP Tue Mar 1 13:49:40 UTC 2011 i686 GNU/Linux

Notice the i686 in the code, that means your machine is 32-bit.

UPDATE:

Type in the following in the terminal;

uname -m

It will give you either x86_64, which is 64-bit, or something else, which is 32-bit.

uname -a

_64 will mean that its 64 bit. otherwise its 32 bit