Since this is an Ubuntu forum, just for the record i prefer Linux over Microsoft products and am a happy longtime Ubuntu user
I run several computers on a business network, three of which still use WindowsXP on the internet on a daily basis with no problems or security concerns. Microsoft still provides monthly security updates and has commited to ongoing critical update support until April 2014.
Sounds like you have a triple boot computer but not a single operating system allows you to fully complete your work, plus you had a partially unsuccessful BIOS update:
WindowsXP has virus problems
SolusOS 1.2 doesn't work properly
Ubuntu has a problem with random lock-ups
Since you're reluctant to run WindowsXP, why not boot and run your system from a Linux live CD for a few days to see if you still expereince random lock-ups (eg. Ubuntu liveCD, Puppy Linux).
If still random lock-ups then you probably have a hardware issue. Either run the appropriate software to test your hardware (eg. ram test, hard drive scans, etc) or replace/upgrade your system or specific components. Windows and Linux have good tools to test your ram and hard drives...not sure if you've recently tested your hardware?
If no random lock-ups then just your operating system installs aren't working properly. In this case, you might consider reformating your hard drives and installing fresh operating systems. For me a fresh install is always a last resort but in this case it may be warranted. I'm presently using an Ubuntu install that's >5 years old and it works great every day.
Just my thoughts. Your system you decide but it does not sound like you are very happy with it's present performance anyways.
In regards to your SolusOS upgrade comment, it is possible your system may have developed a hardware problem around the same time you attempted to upgrade to SolusOS 1.2.