Woopdidoo. Brand new day, sunshine, weekend within grasp, I am in a glorious mood. =)
Let´s go.
AchViz = Architectural Visualization. It requires a high render capacity, architectural knowledge, or at least a floorplan, lots of experience with materials and light if it whould look photorealistic.
Then, you shouldn´t have instulted anyone in the first place, but thats my opinion.
As well as for the caps, proofreading is a blessing. I usually proofread my text, not that it would help =) but I guess its a habit as english´s not my native language.
Your particle system. It´s like fixing a computer without being there, the nightmare of everyone having a friend call with the words “I got a problem with my computer…”.
Post up the blend in your thread and I can look at it, although in the one with the hectic cam, I unfortunately don´t really see what the problem is either.
One suggestion, look at camera shake scripts, there are plenty around and it looks cool when the cam shakes on ignition. But basically without .blend I can barely help you there.
Fact is, I barely use 2.5 atm, just playing with it, and encountering any problems might as well be due to bugs. If you find something cheesy, look up here : https://projects.blender.org/ to see if you have ran into an reported bug.
I work with Blender, I can´t rely on an alpha/beta, I need a stable working environment so I am still with 2.49b.
Ray the robot, I basically like, but this one, as many of your other projects, have the same problem, you drop it at some point and restart them or completely change them…
You need to get a workflow going. As for Ray, start with concept arts.
Draw different heads, different bodys and other parts and then make one final concept and model him.
I don´t think Ray would look cool with the current head posted in that thread.
Get a clear line in your projects, and don´t start everything at once, nothing will get finished and all your threads will ebb away. Focus on one thing at a time, you´r stepping into too many areas, that are even seperate jobs in the industry.
I know its exciting and you want to rebuild the world in a day. Most of us have been there =)
But it will do you no good.
Actually your system is a bless, you should learn to circumvent the limited resources, by tweaking rendersettings, cheat with reflections and stuff. Often enough you need it.
If you got to render a 5 min short, which are 9000frames in 1080p.
If you save 2 minutes on each one for cheating reflections for instance, you save 12,5 days rendertime if you´d render on one machine. Save another two minutes by using appr. AO instead of ray. AO, another 12,5 days and you already saved 25 days rendertime on one machine. If you got to pay for a renderfarm it sums up. If you run your own farm, you still can save a day or two.
Brings me to the next point, for your renderings, you might want to get rid of raytraced ambient occlusion, that is what is causing the grain in your renders, and your machine isn´t meant to render 6+ iterations to get rid if the most noise. Switch to approximated AO, even 1 pass gives nice results and its 100 times faster than raytraced.
Next, post up one of your blends already and tell whats wrong with the rendering or if it is one that is not rendering. Looking at your rendersettings would help you alot.
Don´t get me wrong, the new computer would most likely enhance the overall performance, but if you can still use this one, you can use the money to get, i don´t know, an artpad, some books or training dvd´s. You can also check your machines performance yourself. go there:
http://www.eofw.org/bench/
render the benchmark scene and compare your rendertime with the ones posted there, then you see how your machine performs and you can determine if your rendersettings are off, or if it is indeed a problem with your machine.
And reading in your other threads that rendering a cube takes forever already, my guess, given by your approximated computerspecs, is simply, that you mess up your rendersettings.
For your work with particles, particles and all kinds of physics simulations require a vast amount of system memory, I doubt you have beyond 4GiB and i guess you run 32b blender. If you run complex particle systems under 32bit or try to render them blender will crash, out of memory.
If you use too many composting nodes in 32bit blender it will crash, out of memory.
For your latest crash 
ctrl+w is your friend.
I save everytime before I testrender, run a viewport animation, basically on everything, cant afford to loose any work.
To simply testrender your scenes to get visual feedback, turn of raytracing in the render tab.
To render with your current settings and get feedback on some lighting or material, use the border render (shift+b in camera view)
For particle systems, on your machine, don´t display 100% of the particles as it is set by default.
There are a gazillion things to do and not to do and its hard to say what you can do and what not and what you do wrong and what not. Explaining all would equal writing a book, and there are people here that are more fit for that task.
I can just look at your files and tell you whats wrong, If you got specific questions I might be able to answer them.
As for my rudeness, Richard got it pretty much, many got probs with it in real life too, but its a problem of society not mine.
I am blunt, honest and straight forward. Usually I got no time to talk cherries on the cake and don´t even care to do so. =)
I just giftwrap stuff if it could really hurt somone, but most of my friends know what they get when they ask me, and actually apreciate to get straightforward feedback. Even if it hurts. I also don´t cheer if someone bashes my work.
Happens in the job often enough. You work your brain out for days, think thats awesome stuff, but lost all the distance to the project, go to the next meeting and the mediadirector says…
“naaah… thats too green, not mystic enough, there the animation is too slow”
first thought “wtf… you sob… murmur”.
Then you redo it, get back to the next meeting…
“naaah, thats too red, too mystic, and the animation is too fast now”
pullmyhairs
The next time you bring it in, all seems perfect, your pride broken into pices but you took it like a man.
Then you dig out the first version and compare it to the final one and think…
WTF was i thinking… thats utter crap i produced there… good I got straight forward input.
And you already have been there yourself… look at your Zappergun thread =) you noticed yourself how awesome your dug out renders where =) And that is just because you evolved your skills, you haven´t got any blunt C&C on it.
I am sure I forgot something I wanted to say, but this post´s too long already.
If you read until here without falling asleep, thanks for reading =)
And now I go back to my demon… Human topology - time to get project Natsuki forward, the only personal project I got at the moment and which i barely got time for. 
Could earn you some serious money.
