I'm sitting here with a Ultimate box.
Minimum requirements:
800MHz processor.
512 MB RAM.
20GB HD.
15GB free space.
Super VGA graphics.
CD-ROM drive.
Recommended:
1GHz 32-bit or 64-bit processor.
1GB RAM.
40GB HD.
At least 15GB free space.
DirectX 9 graphics with WDDM driver, 128MB RAM, Pixel Shader 2.0, 32 Bits per pixel.
DVD-ROM drive.
Your 445MB doesn't reach that, and their 546MB only gets through by the skin of their teeth, causing low effect detail and poor performance.
I was able to run Windows XP Pro off of 256MB of ram and could play a few games on it. Granted it was mostly Grim Fandango and Curse of Monkey Island. Hardly recourse consumers.
XP doesn't need much memory, 64MB to be exact.