I AM an avid Windows user. But I am also forced to use DOS programs - either because there is no Windows version of a program available or because my company is too cheap to upgrade its DOS program for Windows. My problem is trying to run a DOS program from within Windows. Supposedly, you can click on the MS-DOS icon to run DOS; when the DOS program finishes, you return to Windows. This does not always work. I keep running out of memory. Also, the DOS program hogs the computer so I cannot see the Windows program that is running. MATTHEW LIE Tsuen Wan The problem you are experiencing occurs because of the way Windows runs DOS programs. Windows is a software layer that sits on top of DOS and protects users from the cryptic commands associated with it. When you ask Windows to run a DOS program, this is referred to as ''shelling'' to DOS. But instead of Windows removing itself, it loads in another copy of DOS. That means you have a bulky ''sandwich'' of DOS, Windows and DOS again. The price you pay is the memory gets eaten up. Chances are this is why you are so quickly running out of memory. Landmark Research International Corp offers a nifty little utility program appropriately called DOS for Windows. It lets you run DOS programs from within the Windows environment. When it is activated, a DOS window appears on the screen. DOS for Windows allows you to size the DOS window to fit the space you want and lets you operate most DOS commands and programs without adding another layer of DOS on top of Windows. The result is that you can run more programs without running out of memory. You can also keep Windows applications in view while you run the DOS programs. DOS for Windows offers more than 60 DOS-compatible commands. DOS junkies can even use it instead ofthe Windows program and File Manager. DOS for Windows sells for US$49. For more details, write to Landmark Research International Corp, 703 Grand Central Street, Clearwater, Florida 34616, USA. You can also fax the company on (813) 443-6603 or telephone it on (813) 443-1331. If, however, you do not fancy spending US$49 on this software, plus the extra on postage, look for a shareware program also called DOS for Windows on local bulletin board services called Houston BBS (dial 735-0613).