Problem for converting huge png into jpg.

Hi, I made a pretty huge image (60180x30096x16M) in PNG format by assembling
lots of tiles, using ImageMagick (convert +append ...).

The image is displayed without issue my ACDSee Classic, but IMDisplay report
the following error message:
IMDisplayDoc function [DoReadImage] reported an error.
imdisplay.exe: Corrupt image `T:\Nice01-23.png' @ png.c/ReadPNGImage/2981

I also have errors when trying to convert the image into jpg with:
T:\>convert Nice01-23.png Nice01-23.jpg
convert: unable to extend cache `Nice01-23.png': No space left on device @
cache.c/OpenPixelCache/4029.
convert: IDAT: CRC error `Nice01-23.png' @ png.c/PNGErrorHandler/1455.
convert: Corrupt image `Nice01-23.png' @ png.c/ReadPNGImage/2981.
convert: missing an image filename `Nice01-23.jpg' @
convert.c/ConvertImageCommand/2838.

I am on windows XPSP3, and the T:\ drive has 113GB available.
The Nice01-23.png file's size is 750MB.

T:\>convert --version
Version: ImageMagick 6.5.8-8 2009-12-18 Q16 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2010 ImageMagick Studio LLC
Features: OpenMP

Any idea about what is wrong?

Eric