This will be difficult to do since your target disk is smaller than your source disk. You won't be able to simply 'dd' one disk to another. You'll have to 'dd' the first two partitions then create a new reiserfs on the 3rd partition and tar/untar from one to the other. Very complicated and probably won't work anyway... ;-)
I'd strongly recommend just buying a new HDD that's bigger than the one that's inside!
- K.C.