For users of IBM Personal Computers and compatibles, memory is one of the biggest problems these days. Older machines with 256 kilobytes or even 512K of random-access memory don't have enough to run many new programs or even the new versions of old programs.

If you have a newer, more powerful machine, such as one with an Intel 80386 processor, you need several megabytes to run software such as Windows 3.0 or the latest version of Lotus 1-2-3.

More memory lets your programs run faster, lets you work on larger documents and lets you run more programs at once -- saving work time by letting you quickly switch from one to another.

There's a software problem, though. The MS-DOS operating system by itself can use only 640K of memory. That's not enough to run the latest big programs.

Even programs that will fit into 640K are sometimes squeezed out by all the various memory-resident utilities -- from mouse drivers to calculators, note pads and network programs -- that many users also place in memory.

After loading DOS and those memory-resident tools, the original 640K might drop to 400K -- too little for many programs. Even those programs that do load may not be able to work on documents of any significant size.

A few years ago, major computer firms came up with various special hardware and software tricks to get around the 640K barrier. Eventually the tricks settled into a standard, called EMS 4.0 for Expanded Memory Specification.

Many programs were rewritten to use this "expanded memory" to find and store their program code and documents in chips on plug-in boards that were organized in line with the EMS standard.

Since that time, PCs built around the 286 and 386 processor chips have become more popular. Unlike the 8088 and 8086 processors in the original PC and XT (and compatibles), the 286 and 386 machines (ATs and AT compatibles) had the right hardware for another kind of memory organization, called "extended memory."

Expanded memory and extended memory start with the same basic chips but organize them in different ways.

Programs that use expanded memory can't necessarily use extended memory, and vice versa. But whether you decide toget more expanded memory or more extended memory, you could end up spending a lot on memory chips. Putting a 4-megabyte memory expansion card into your computer could cost more than $1,000.

For that same $1,000, though, you can buy 200 megabytes or so of hard disk. Add a utility program that will make the processor think some of that disk memory is expanded RAM, and you have a software solution to your memory problem.

Using disk space as expanded memory, however, won't buy you all of the speed of true RAM memory because a disk drive operates much more slowly than RAM. But if this trick lets you load larger programs and files than you could otherwise, it can still be worth it.

Above Disc ($119, Above Software, (714) 545-1181) can transform extended memory or disk memory into expanded memory. Either way, it works automatically, providing expanded memory to whatever programs you have that can use it.

Installation is easy. There's a program with Above Disc that asks you how much of your disk or extended memory you want to convert to expanded memory. It then puts the appropriate files on your main floppy or hard disk. It can also slide the right instructions into your DOS configuration files, so that Above Disc will be active as soon as you start your computer.

The Above Disc program takes up 80K of memory in a PC or XT, but that's not so bad because you're getting more memory back in the bargain.

In some ATs, it can use as little as 2K. And there's a special command that lets you hide Above Disc's expanded memory from programs that wouldn't be able to handle it.

The latest version of Above Disc -- 3.1 -- also comes with three other memory utilities. There's a 1-2-3 add-in version of Above Disc that uses only 11K (instead of the 80K overhead of the regular Above Disc) while turning extended memory into expanded -- but just for 1-2-3.

The AboveLAN utility is for Novell network users who have 286- or 386-based systems with 1 megabyte of RAM installed. It loads the Novell NetWare driver -- the software that must always be in memory for your computer to connect to the network -- up into some memory beyond the 640K. That can give you 360K more memory to use on top of your 640K, even without using extended or expanded memory.

The other utility will work on any PC, XT or AT that uses an EGA or VGA graphics controller. Above640 will steal as much as 96K of RAM away from these controllers and give it back to you for regular DOS use. In other words, you'll have 640K plus 96K, or a total of 736K without resorting to extended or expanded memory.

Unfortunately, you can't run graphics programs with this memory -- EGA and VGA screens need that stolen memory back to run graphics programs -- or even the graphics parts of a program like 1-2-3.

The manual comes with a list of programs that don't run well with Above Disc, including Adobe Illustrator, Allways 1.0, part of PC Tools 5.0, Codeview, Javelin, Lotus HAL, Oracle and Windows-386 (the version before Windows 3.0).

Some other programs -- such as Clipper, DisplayWrite 4, Publisher's Paintbrush and Ventura Publisher 2.0 -- work well only on 386 machines with Above Disc in its 386 configuration.

(Of course, all these memory organization and configuration hoops are one more reason to like the Macintosh. On my Mac, you just buy more chips and plug them in.

The system software knows they are there, and all programs have their own window for instruction in how much of this memory to use under the MultiFinder. No "extended," no "expanded," no "high DOS memory" to worry about.)

If you have a program that needs or can use expanded memory, a utility such as Above Disc is the least expensive way to get it. There are competitors to Above Disc, such as Biologic's VRAM, and some of them cost less -- VRAM runs only $49. But Above Disc does the job well, comes with the 1-2-3, NetWare and Video RAM utilities as extras and installs quickly and painlessly.

Phillip Robinson is an author of books and articles about computers and an editor for Virtual Information of Sausalito, Calif.