i have downloaded BT3 extracted it using winrar runned the bootinst.bat file copied both folders to my Formatted flash disk setted up my pc to boot from flash, and every time i try to boot BT3 i get a black screen saying "boot error" tied it on other pc same thing got a black screen saying "missing operating system" tried unetbootin-windows-357.exe same thing.
any body got any idea why im not able to boot BT3???
thanks

I had a similar problem. I have 3 desktops and a laptop. The usb would boot on one desktop (not the newest, not the oldest) and nothing else. I asked in the backtrack irc channel (freenode #backtrack) and they told me all these crazy things about the filesystem type and copy modes or something. I believe it basically ground down to that you can create the usb install on windows or linux and doing so on linux seems more reliable. I guess that you used windows as you mentioned using winrar. There is a tutorial somewhere on the backtrack website about creating the usb install and i believe it has instructions for both windows and linux. Maybe try the linux guide?

I created on linux and its working perfectly.

thnks

i have ubuntu on the same pc ill try it there thanks