Processing Large Images

New to this group. I'm using a Pentium4 computer w/ 1.024GB RAM. I
have a new STL11000 camera and am having trouble processing the large
files (20.4MB each). In CCDSoft, I can join files to make an LRGB
image, but the computer locks up when I try to save the file. In
AIP4Windows I can not load four images simultaneously to make an LRGB
picture; the fourth just loads up blank. I can resample the pictures
to 90% of original size and work with them in AIP, but then I get some
artifacts. Please advise; what software can be used to process these
large files.

MikeW