Video game says I don't have enough GB?

I'm trying to play Vampire: The Masquerade on Steam, I have played it before but on a different computer. This one it will not run (Sims 3, skyrim, fable 3, smite, Dead space, and Minecraft all run fine) every time I try to open it, it says "Can't run less than 15GB available!" Thing is, I have 460 some GB on my hard drive free, If its referring to my RAM I only have 3.45GB available but my Ram only has a total space of 4GB but I don't know what game in this world requires 15GB of Ram o.O What do I do?

Try freeing some space in your windows drive.

If you have Windows 8 operating system, it hates old games.
Any mods?
Running the game as an Administrator?
Running the game in a Mode (XP, Win98)?
Installed to the C:/ (default) drive?
Compare your machine specs. Does it meet these.
System Requirements
Minimum System Requirements
Processor:1.2GHz
RAM:384MB
Video Memory:64MB
Hard Drive Space:3.3GB
Operating System:98/ME/2000/XP
DirectX Version:9.0c
Recommended System Requirements
Processor:2.4Ghz
RAM:512MB
Video Memory:128MB
Hard Drive Space:5GB