Windows Tips

Mode About You

Your software may be slowing down your hardware without your knowledge. A slowdown can occur in Windows 95 and 98 when the operating system has to use real mode (an older memory scheme associated with DOS) to run 16-bit drivers or other system software instead of using protected mode (a 32-bit memory scheme that can isolate programs in memory to prevent conflicts).

To find out if your system is dropping into real mode, right-click My Computer and choose Properties. Then click the Performance tab. If you see the line 'Your system is configured for optimal performance', then you're running everything in protected mode. If your system has one or more devices running in real mode, they'll be listed--in a box on the same screen--as using MS-DOS compatibility mode (see FIGURE 3). If you don't see any mention of MS-DOS compatibility, you can rest easy. Otherwise, pay attention. The nitty-gritty of MS-DOS compatibility can be complex, but here are a few tips to get you started on troubleshooting and performance-tuning in this situation.

Diagnose it, part 1: The Performance tab is your first line of defense in discovering the cause. Often a Details button is present, but clicking it usually provides minimal or vague information. More helpful is the actual list of items using compatibility mode. If you see the problem driver file name listed, you're halfway home--unless you don't know where the driver came from. Sometimes you can guess which device it's associated with by opening the driver in a file viewer or word processor and looking for a manufacturer's name amid the gobbledygook (don't save the file when you're done looking).

Diagnose it, part 2: On the other hand, if a device is listed but its driver isn't, click the Device Manager tab and look for the device (or for any adapter it may be connected to) in the list. If you find it listed with a yellow exclamation point, double-click it to see its properties, which should provide information on the problem. If the problem is a resource conflict, find IRQ or DMA settings that don't conflict with other devices, and consult the device documentation for help. For help with other problems, keep reading.

Troubleshoot it: MS-DOS compatibility mode (and yellow exclamation points in Device Manager) can crop up if someone deliberately turns off protected mode support for your disk drives (for example--paradoxically enough--while you're troubleshooting). With System Properties' Performance tab still visible, click File System and then click the Troubleshooting tab. If 'Disable all 32-bit protected-mode disk drivers' is checked, you may have solved the mystery. But before unchecking this option, ask around to see who in your office or home checked it (it's off by default); the setting may have been necessary to get your system working.

Update it: If the problem stems from a driver, make sure you have its latest version, which is normally available on the manufacturer's Web site.

Unplug it: In many cases, the software causing Windows to use real mode is launched from your autoexec.bat or config.sys files. If the list in the System Properties' Performance tab doesn't give you enough information, you can make backups of autoexec.bat and config.sys and then analyze them in a text editor like Notepad. As long as the device in question isn't the disk drive you boot from or some other vital instrument, you can safely type rem (followed by a space) in front of the line you think is launching the problem software. Then save the file and restart your computer. (Always keep a bootable floppy nearby in case you have problems starting your system.)

Return to the System Properties dialog box to see whether Windows is still in MS-DOS compatibility mode. If the performance tab says your computer is configured for optimal performance, you've found the culprit. If everything else on your system is functioning well, it probably means that Windows Setup failed to disable the "legacy" line in config.sys or autoexec.bat--just disable that line yourself. In theory, Setup should remove from these two files the lines that call drivers for which there are new, protected-mode ones. However, if a device (such as a CD-ROM drive or SCSI device) ceases to be visible or to function, go to the next tip.

Add it: If the device listed on the Performance tab is missing from the Device Manager tab (or if a drive is missing in Explorer as a result of the previous tip), and wasn't detected by Windows when you rebooted, choose Start, Settings, Control Panel and double-click the Add New Hardware Wizard to reinstall the device with the proper drivers.

Sterilize it: If the System Properties' Performance tab cites 'mbrint13.sys' as the problem driver and you're not using disk-management software (see the "Update it" tip on previous page), you may have a boot-sector virus. Get an antivirus program capable of detecting and killing such beasties. Our recommendation: Symantec's Norton AntiVirus, downloadable from FileWorld.

Live with it: A few devices actually work better in real mode. For instance, some disk drivers support encryption only in this mode. If you need such functionality, find the corresponding devices listed in the System Properties' Performance tab.