I just got this computer. I had the game earlier.
:(
If I were you, I'd just buy a drive and install it - if it's a desktop, you can get a decent internal drive for less than you'll pay to download New Vegas off Steam. If it's a laptop, you can buy an external USB drive for it. It'll cost more (around $70 - $80), but it'll be a very useful thing to have anyway, for more than just playing games.
Also, the new Vegas download is huge - about 5 GBytes IIRC. If your ISP limits your data usage, that could get
real expensive quickly.