The Sun Enterprise 250 is a very old machine. I think it usually has two 400 megahertz processors and 1GB RAM and a CD-ROM drive, right? I recommend installing Solaris 9 with a CDE desktop and staying away from Solaris 10 or OpenSolaris because they might run a little bit slow, especially with a massively bloated and overweight GNOME graphical desktop on them (it's like running Windows Vista Aero on a Pentium II). Solaris 9 with a CDE graphical desktop or some other similar light weight desktop (maybe XFCE?) should be fast on that thing though.
Also, old Solaris is not the only operating system that runs well on ancient SPARC hardware. The latest and greatest builds of OpenBSD and NetBSD run blazingly fast on old SPARC hardware too and might be more along the lines of what you are looking for in a desktop or server operating system because they are more easily available to download and have more up to date packages for things that I like to use a lot in my daily work such as Postfix, git, arping and XFCE than Solaris 8 or Solaris 9 do. The Sun "Enterprise 250" hardware is fully supported by OpenBSD as you can see by going to this link: http://www.openbsd.org/sparc64.html There's also an open source OpenSolaris distribution developed by a really smart guy who hangs out on this forum named "Martin Bochnig" that I heard runs well on ancient SPARC hardware. I think Martin's distro used to be called "MartUX" but I don't know if it's still called that or if it's now called something else. It might be worth while if you can find Martin on these forums to ask him how well he thinks his operating system will run on your hardware. If you want to try installing Solaris 9 on the Enterprise 250, you'll probably want to check this free e-book that's available for download on the internet called "Learn Solaris 9 Through Step by Step Lessons" by Steven Beebe. I think it might still be available at one of the following links: http://www.teachmesun.com/ or www.sunfreeware.com/Free-Solaris-Ebook.pdf.gz Steven Beebe had this Solaris 9 web site called www.teachmesun.com but it doesn't seem to be available right now (maybe he's having financial difficulties?) but if you can track him down, try to give him a donation for that book because I learned a lot from reading it and you probably will too. Some other good Solaris 9 books if you are a total Windows noob starting out on UNIX (i.e. Solaris 9) are the very hilarious and very awesome "Complete Idiot's Guide to Solaris 9" by Martin C. Brown (Martin if you're reading this I'm buying a pair of sandals and working on growing a thick beard so I can be a true UNIX guru like you), which is available in incomplete form as a google book or via e-bay or amazon (google book link follows below): http://books.google.com/books?id=H7Wl-xbQKEsC&pg=PA17&lpg=PA17&dq=complete+idiot%27s+guide+to+solaris+10&source=bl&ots=EgDCCiHvYN&sig=FpKov-2GvJJ0Lg9_F5wGoo_5BGI&hl=en&ei=G6I4Srq3F5S2swOm3PC2Bw&sa=X&oi=book_result&ct=result&resnum=4#PPP1,M1 and "Solaris 9 For Dummies" by Dave Taylor (available from Amazon at the following link): http://www.amazon.com/Solaris-9-Dummies-Dave-Taylor/dp/0764539698/ref=sr_1_1?ie=UTF8&s=books&qid=1245225420&sr=8-1 out the following links: You should also probably check out the docs and following links for some additional tips on installing Solaris 9: http://docs.sun.com/app/docs/doc/817-0491 http://www.idevelopment.info/data/Unix/Solaris/SOLARIS_Installing_Solaris_2.9.shtml http://www.osnews.com/story/2299/Review_of_Sun_Blade_150 http://www.computing.net/answers/solaris/how-to-install-solaris-9/4636.html However, you might also want to go to these other web sites below and look at the instructions if you want to get an idea as to how to go about installing OpenBSD on it (OpenBSD is a VERY secure operating system, and you can do very advanced networking related things with the "packet filter" firewall on it that are difficult to do even with thousand dollar CISCO devices): http://www.openbsd101.com/installation.html http://www.openbsd.org/sparc64.html http://www.osnews.com/story/6892 www.chuug.org/talks/20040727/obsd-sun-fw.pdf -- This message posted from opensolaris.org