The answer is maybe
What partitioning scheme do you have? What filesystem? Do you want to try raid0?
The reality is that I hardly think that partition magic or any software can magically extend a partition to another drive. This is exactly what raid0 is.
That said, you can either make the new drive /usr and try to reclaim the /var partition on your old drive (this is iffy for me but....), try some symlink magic and resign yourself to wasted space or simply copy your 2 gig to the newly partitioned 4gig.
I don't want to start a religous partition war but this is exactly why I tell people not to go crazy with partitioning, especially with only one drive, you don't really buy much... most of the time.
I have a single drive system partitioned as follows (this is MY system and an example only):
/boot about 20 megs
/var 1 gig or more depending on your disk size
/tmp 1 gig or more depending on your disk size
swap (with Oracle -- 1 gig) or else 500meg or so
/ all the rest.
This way when my oracle partition fills up I can simply add another drive and then mount it. No wasted space and minimal hassle. The same for anything else
The reason for /var and /tmp on seperate partitions is the fact that if you don't seperate them and one fills up... error city. Your system, while not dead, might as well be.
One of the great things about Linux that I hated in the BSDish OS's is the fact that root is automatically a seperate partition and therefor you can at least log in if the /var or other partitions are full.
If you are not using linux, you may want a /root partition also.
