Merge 2 partitions of different physical disks

I have a good sized HD that has WinXP. I did not want to fuss with that drive but wanted to install Ubuntu. So I bought a USB (500G) disk and partitioned it. 100MB when to a bootable linux partition (ext4) and I left the remainder ntfs. Ubuntu was installed on the new disk. Next, I set the computer bios to boot from the USB. When booting, grub2 has a boot screen which allows me to boot into ubuntu or XP (Since I like ubuntu, I set that the default after 10 seconds). Now I have a full ubuntu and XP and never touched my XP HD. Also, if the USB is not plugged in, XP will boot. It seems you might be able to do the same thing or similiar and leave your main disk on the acer untouched. But maybe you have other considerations.
jlp

This is a common problem. One solution is to copy over the partition to the new disk (http://www.arsgeek.com/2008/01/22/how-to-clone-your-bootable-ubuntu-install-to-another-drive/). Be careful though, the 'dd' program is notorious for being very particular about its input (some have even joked that it stands for 'delete disk'). You must be particularly careful that you have the 'if' and 'of' arguments right: switching them up could render the contents of your current disk inaccessible. Also, you didn't specify, but it is essential that the data on your 120 GB disk is not important to you anymore, if there is anything on there at all. Also keep in mind that someone after me might answer this question in a more Ubuntu-centric manner, in some cases there are particular ways to do things.

Just a little more ...
You can't "merge" two partitions because they are physically separate. However Unix (and Linux) do support file links and mounting of filesystems in a folder. A link to a file will have the file name in a directory but the file itself is somewhere else and can possibly be on a different disk. So you can create a directory in a folder that actually exists in a different place. For example, your user directory is probably in /home/yourname. Now "yourname" could be a link to another mounted disk. It looks like your directory is in the usual place but the data is actually elsewhere. This was invented to ease usage when disk sizes were small and you needed many of them for a medium to large system. But administration can get to be a headache when you try to split system directories across multiple media. It can be done. Try to keep all root related stuff together because some code might not be happy with links. G'luck
jlp