Newbie needs answers...

i really need to kno how to lst. im growing in a small area w/ a halogen light which is about 6 in from my plant and i have a fan on it.
i just topped it a week ago and put it into flower 2 days ago...
i was wondering y my leaves r turning yellowish??
i havent used nutes the wholeway throug veg and i dont have any for flower. am i doomed.

Get yourself some inexpensive CFL's (compact florecent lights). Halogen is no good for plant growth, as it doesn't produce the correct spectrums of light. Keep the fan on it. How old is your plant? Also, what type of medium (soil) are you using? Yellow leaves can be a sign of a wide variety of problems. We just need to know more about your grow. Maybe some pictures?

im jus using some potting soil i bought from lowes...
and i am growing in a speakerbox.. my plant has been growin in veg for about 2 months from bagseed and it didnt get really bushy so i topped it and then started to train then put it on 12/12... am i doomed??? oh and im located in northern us...

If some of the lower leaves are turning yellow, that's normal. If top and mid-level leaves are turning yellow, it could be a wide variety of problems. Some pictures would really help us out a lot. I would not say you are doomed, but you definatly need to get more and better lights on your plant. Also, this may be a good time to start feedin some nutes, as your soil has lost a lot after 2 months of veg.