linux

[comp builder]

I went a friends last night and saw he had windows and linux installed together, he had the option which one to load on start-up. How do i do this? can i save both operating systems on one hard drive?
also i have my system overclocked, this may sound stupid but, would the overclock still work when i'm using linux?
also what is the benifit of linux, from what i can gather it loads and runs faster, dosn't it? is there any other benifits?
thanks

 

[comp builder]

which is the best to download?
i thought maybe slackware but none of their mirros are working, so now i'm stuck. Anyone know which is best and can provide a link
thanks

 

[comp builder]

i thought ubuntu was for servers?