Xfree86 memory consumption

Hi,

I've just buy a new PC. This one have a:
- Geforce4 ti 4200 64Mb
- LCD screen
- "only" 256 Mb RAM.

So, I'e installed a DEBIAN GNU/Linux woody (xfree86 4.1.0-16).

My problem is that the XFree86 use 256 Mb of memory. The top status is:
   469 root      10 -10  268M  12M  4660 S <   0.5  4.9   0:02 XFree86

What goes wrong?
What can I do to have a smaller XFree86 server?
(in a time, only 16Mb were necessary to run Linux with X)

My XF86config is attached.

Thanks for any solution reducing the memory size.