I have just been through the trouble of trying to get my nc10 netbook to install XP off a USB stick. That failed, so I came up with a cunning plan.
NOTE: This will require the loss of all data on the external drive, so make sure you have everything backed up. You also need a fully licensed copy of XP.
Please read through this whole guide before attempting this, as you need to know what you are getting yourself into.
1. Download the Windows 7 RC ISO file.
2. Download and install powerISO or other virtual drive software.
3. If using Vista as the setup machine, run diskpart as administrator.
4. Type 'list disk' and then choose the external drive by typing 'select disk #' where # is the disk number. Then hit enter.
5. Type 'clean'. And hit enter.
6. Type 'create partition primary', and hit enter.
7. Type 'format fs=NTFS' and hit enter
8. Type 'assign', and hit enter.
9. Type 'active', and hit enter.
10. Type 'exit' to exit the diskpart software.
11. Copy all the Windows 7 setup files off the ISO mounted in the virtual drive onto the freshly prepared external drive.
12. Insert (or mount) an XP install disk (the version you require).
13. Create a folder on the external drive (call it XP).
14. Copy all the XP setup files into this folder.
15. Plug the external drive into the computer you want to install XP onto, and boot up the windows 7 setup. You may need to change your boot priority settings for this to work.
16. When the setup screen loads, press Shift + F10. This will open a command prompt.
17. Type 'd:' where 'd' is the letter assigned to your external drive. And hit enter.
18. Type 'cd XP' and hit enter.
19.Type 'cd i386' and hit enter.
20. Type 'winnt32.exe' and hit enter.
21. Follow through the setup, and select 'Choose drive letters and partions during setup'. Make sure that it is ticked.
22. Follow the install through, making sure the external drive is plugged in the whole time.
23. You should now have an XP install on your computer.
If it wont boot, and says 'Operating System Not found', follow steps 3 -11. Then get to the setup screen and hit Shift + F10.
1. Type 'diskpart' and hit enter.
2. Type 'select disk 0' and hit enter. (If disk0 is the disk you installed XP on).
3. Type 'select partition 1' and hit enter. (It should be partition 1, unless you changed it during setup).
4. Type 'assign' and hit enter.
5. Type 'active' and hit enter.
6. Re-boot the machine without the external drive attached, and you will have a fully booted copy of windows XP.
NOTE: You will have to repeat this whole process for each time you want to install XP, as the XP install method wipes out the Windows 7 setup boot manager.
NOTE: This is only nessisary if you don't have a cd drive, or cant get hold of one by any other means.
You can use a USB thumbdrive for this, but it requires changing some of the XP setup boot files to load USB drivers. There are plenty of websites that will tell you how to do this. Google is your friend.