The problems may or may not be unsurmountable, but you are going the wrong way about it. You are all over the place with partitions and hardware and are bent on making this work your way, just because you could install Solaris in a class box some time ago.
That you have other OSs working on your hardware means nothing. No matter how many times you say you can use SuSE ort Mandriva or whatever, it means nothing. So stop posting it.
Whatever computer you use, I would suggest to you 3 things:
1.- VERIFY THAT YOUR HARDWARE IS LISTED IN THE HCL
Solaris OS: Hardware Compatibility Lists
2.- AFTER you have VERIFIED that your hardware is in the HCL, install Solaris by itself first. Learn what happens when you install it.
3.- THEN, there are plenty of tutorials about dual booting a box with Solaris and something else. The Sun Bigadmin site has a couple, like this one
BigAdmin Submitted Article: Quad Boot With Windows, Sun Java Desktop System, and the Solaris Operating System