RobbieD, there are a lot of articles on the internet about room acoustics. Having seen your topic about buying a $1000 microphone, I suggest reading this two page article for a quick overview of the topic you would do well to understand:
How to Record Vocals Part One | DV Magazine
How to Record Vocals Part Two | DV Magazine
In order of importance for making a good-sounding vocal recording:
1) A good singer!
2) The correct acoustic environment, which includes the mic’s pop shield and mic placment.
3) The type of microphone.
4) The type of microphone preamp.
5) The specification of the recording system or audio interface (assuming some form of digital recording)
You will get a better sound out of a larger room than a small closet, so use the room you currently have your computer and musical instruments in, using suggestions from the above article about how to treat the area around the microphone.
My personal opinion is that you will probably get a better sound if you spent something like $250 on a microphone
(eg. Rode NT1a), $250 on a mic preamp (if your audio interface doesn't have a suitable mic input, and the rest on acoustic treatment.