The nation's 115 million home computers are brimming over with personal treasures — millions of photographs, music of every genre, college papers, the great American novel and, of course, mountains of e-mail messages.

Yet no one has figured out how to preserve these electronic materials for the next decade, much less for the ages. Like junk e-mail, the problem of digital archiving, which seems straightforward, confounds even the experts.

"To save a digital file for, let's say, a hundred years is going to take a lot of work," said Peter Hite, president of Media Management Services, a consulting firm in Houston. "Whereas to take a traditional photograph and just put it in a shoe box doesn't take any work." Already, half of all photographs are taken by digital cameras, with most of the shots never leaving a personal computer's hard drive.

So dire and complex is the challenge of digital preservation in general that the Library of Congress has spent the past several years forming committees and issuing reports on the state of the nation's preparedness for digital preservation.

Jim Gallagher, director for information technology services at the Library of Congress, said the library, faced with "a deluge of digital information," had embarked on a multiyear, multimillion-dollar project, with an eye toward creating uniform standards for preserving digital material so that it can be read in the future regardless of the hardware or software being used. The assumption is that machines and software formats in use now will become obsolete sooner rather than later.

"It is a global problem for the biggest governments and the biggest corporations all the way down to individuals," said Ken Thibodeau, director for the electronic records archives program at the National Archives and Records Administration.

In the meantime, individual PC owners struggle in private. Desk drawers and den closets are filled with obsolete computers, stacks of Zip disks and 3 1/2-inch diskettes, even the larger 5-inch floppy disks from the 1980s. Short of a clear solution, experts recommend that people copy their materials, which were once on vinyl, film and paper, to CDs and other backup formats.

But backup mechanisms can also lose their integrity. Magnetic tape, CDs and hard drives are far from robust. The life span of data on a CD recorded with a CD burner, for instance, could be as little as five years if it is exposed to extremes in humidity or temperature.

And if a CD is scratched, Hite said, it can become unusable. Unlike, say, faded but readable ink on paper, the instant a digital file becomes corrupted, or starts to degrade, it is indecipherable.