Yeah, you can do that. But you will not like it.
Still, you need to get a bigger drive.
If you have a desktop available and the right adapters kyou can put both Windows 7 and XP on one drive with maybe four partition.s
Windows 7 wants two. Give EXP one. An a big partition for your backups, which you will need.
Some of the partition wokr should be done on a desktop.
Don't use UASB adapters. Put the drive into a desktop.
Sorry I am a little slow on this. It's hard for me to correct my spelling and grammar errors. But nevermind that.
I need to explain to you the the right order of things. What you're going to do with a new drive is stick it into a laptop and boot the XP install disk and install XP on to the new drive. But, you want to use that opportunity to make some partitions you want to have a large area that can be used later as a backup area. And you want to leave another large area that's going to be used by the Windows 7. Now the part that's hard to figure out is exactly how Windows 7 is going to rearrange the stuff. Anyway we get to the point where Windows XP is up and running on the lap top and there is an extra partition available and there's a lot of free space available.
Now then, we take the new XP drive out to the laptop put it over into the desktop and somehow are going to try to use one of the partition programs like to the Acronis and try to copy your Windows 7 partition on to the new drive, hopefully they'll be a low space left over in case it's needed.
Now before this I trust issue of already made a Windows 7 recovery CD. We will need that.
So what to do if you put the the XP disk back in the computer and it has the Windows 7 stuff in a partition and of course Windows XP will not know anything about that in your just boot up and Windows XP. Now we know that it's still working, most restarts the laptop with the Windows 7 recovery CD and we will probably need the Windows 7 DVD handy just in case. The recovery CD will try to figure out what you did and reestablish vindication with the Windows 7 installation. This is the hard part. Maybe it will work if it does you now have a dual-boot computer that'll come up and ask you if you want to use Windows 741 earlier version of Windows. And basically that's it. But, the hard part is if you ever damage the XP installation you're in for a hard time.
For you the details I left out of her the other fellows here will fill you in for the parts I might have skipped over. Basically, you're going to end up with a Windows 7 system is not working right because XP was installed first and the Windows 7 is just a copy of the original system. Kind of clumsy.
While, that's one way to do it. May be not the best way.,
But I really do think you should try it with the newer larger drive. That way the original.drive if your backup if everything goes wrong.