Installing Linux
 

Prob 1
I have got Windows XP already installed. Now I want to install Linspire and SUSE 10. So which one should I install first?

Prob 2
I want to use the Windows XP boot-loader as my default boot-loader with the above OSs, so how do I do that?

Well I would install Linspire first, then SuSe 10.

And I would absolutely let lilo be my default boot loader. I have been using it for quite some time now, and I can only recommend it instead of letting the XP boot loader handle it.

Any particular reason for why you want to use XP boot loader? If it's for ease of turning back to a 'clean' XP system it's not a problem if you installed the lilo boot loader.
Nothing that can't be changed in 2 minutes ;)

Why both Linspire and SUSE? Is there really a need for this? Rember, always install Winblows first (which youve done), since it will crap all over any exsisting OS.

Also using the Windows bootloader will no doubt be a hassle and unstable. LILO is tried and true at this exact thing, and will boot Windows flawlessly.