if i install yellowdog linux

would that mean everytime i want to use it i would have to format my harddrive
or is it a case of just changing it via the xmb

and cant windows be installed
and most importantly is it worth the hassle
and would do i need to format my harddrive to install it
and could i boot from a disc instead of wasting HDD space

and ive already installed quite alot of demos (actually installed not just dl) can i copy them to a mem stick and copy them back

1. Linux will boot first and give you the option to go into Linux or the PS3 OS. So no you dont need to erase it every time.
2. Windows doesnt use the same architecture as the PS3. So porting Windows would be hard, even though it has been done. Instead, someone would need to design it from the ground up, with the PS3's multiple cores in mind.
3. No, its recommended though.
4. No, linux needs to be on your HDD.
5. Again, no you cant copy demos to your a external device. Due to the possibility of being able to edit those.

Hope that answers everything, in my opinion you shouldnt install Linux yet unless you need its features. Right about now, most distros dont work great on the PS3. Lacking in either WiFi or keyboard support. Loads of people are developing new ones though, just for the PS3. Like a new version of Yellow Dog and one thats happening on QJ called Media Center. So i'd wait for those.

thanks alot

i might have done it but its taking to long to get the demos
and with some demos theres no need to buy the game lol

There arnt that many good demos worth keeping. Burnout, DMC4 and Skate. But not much besides that.