Umbutu is a Linux distribution. An entirely distinct Operating System, not just a programm.
It don't have any default user name and password, but use those provided by the user.
Can the person from who you got that computer give you the correct user name and password?
If not, it's very probable that it's a stolen computer, and the person who gave it to you is a thief, or the victime of a thief.
If not stolen, then an abandoned computer.
Looks like it originaly was shiped with Windows 98, but the owner replaced that with Umbutu Linux, and got rid of the original hiden restore partition to use it for normal storage. This means that you can't do a factory restore: The image on the hiden partition is gone. This explain the errof you get.
You need to cold boot from an install CD to install Windows XP. In the BIOS, you need to enable booting from a CD, or use a boot floppy it it's not possible to boot from a CD.
That computer may struggle a bit, but should be able to run Windows XP.
There is NO way it could ever run Windows Vista.
Electro, September 2011