Lockups are simple: the machine no longer responds to input and doesn't display any errors. Lockups tend to indicate fairly serious hardware problems and need to be dealt with aggressively, because there is a risk of data corruption and loss.
Unlike Windows 3.x, if a single applications locks up in Windows 95 or 98, it does not lock up the whole computer. You can press CTRL+ALT+DEL to get to the Task dialog box and close the offending application.
Symptoms of a lockup are:
The mouse pointer doesn't move. (Hint: if the mouse doesn't work, try the keyboard; this will confirm whether the problem is caused by the mouse or a lockup.)
Keyboard controls don't work.
The machine seems to be frozen.
There are a few common causes of lockups.
Using incorrect drivers are among the most common causes of lockups and intermittent program crashes. Make sure that video cards, hard disk drives, sound cards, and so forth are using the proper drivers. Always back up old drivers when you are updating, just in case you have problems. That way at least you can go back to a working machine if the new driver locks up your machine.
Lockups created by power supplies tend to be intermittent. The system locks up for no apparent reason-no particular application or function seems to cause the problem. If the power supply is the problem, the errors will show up in MS-DOS, Windows, or any other operating systems that you use.
If a power supply is the suspect, turn off the machine, turn it back on, and walk away for ten minutes. If, after you come back, the machine is still locked up, the power supply is the problem.
Corrupted files are files that have been damaged by bad hard disk drives, floppy disks, CD-ROMs, or corrupted software.
The major symptom of a corrupted file is that the lockup takes place at the exact same time, every time, in the execution of a particular file. For example, suppose that every time you start an application, it locks up when it reaches a certain point. Run ScanDisk to determine whether the problem is with the hard disk. If running ScanDisk doesn't correct the problem, try reinstalling the application in another directory so that it does not write over the same area of the hard disk.
Corrupted files can be created by improperly shutting down Windows. You should never simply shut off a computer; close all applications and properly stop the operating system first.
If you click an icon and receive an "application not found" error, this typically indicates that the software needs to be reinstalled, or that the application has been moved and the icon can no longer find it.
Corrupted Swap Files
Lockups caused by corrupted swap files tend to show themselves when Windows is first starting or when it is shutting down. Turn off the swap files and try restarting Windows. If you can get into Windows, find the 386SPART.PAR file and erase it. Windows will give an error on startup, but it will start up. Defragment the drive, and re-create the swap file.
Bad RAM lockups are easily detected-if a RAM chip is so bad that it can cause a lockup in Windows, the HIMEM.SYS file will detect it. Reboot the computer and watch HIMEM.SYS while it's loading-use the F8 key if necessary. If the RAM is bad, you will see an error message like: "HIMEM has detected unreliable XMS memory at XXXX:XXXXXXXX."
Lockups due to bad RAM chips look a lot like power-supply lockups. Most RAM problems show up as errors or GPFs.
IRQ and DMA Conflicts
Lockups generated by IRQ and DMA conflicts are created when the two hardware devices begin to speak at the same time. Not all IRQ and DMA conflicts manifest themselves as lockups. Remember that IRQ/DMA conflicts don't happen on machines that were "working fine before." Invariably, these lockups take place on computers on which a device has recently been added or changed.
General Protection Faults
General Protection Faults (GPFs-also known to old-time Windows users as "The Blue Screen of Death") fall into four categories.
Memory-management problems show up as GPFs in KRNL386.EXE. Typically, these are found in machines that are running MS-DOS applications and have been incorrectly configured. Pay particular attention to the proper use of exclude statements on the EMM386.EXE line.
GDI (Graphical Device Interface) errors indicate a resource-heap overflow. A GPF caused by a GDI heap overflow can be visually exciting. Typically, these occur on machines with animated screen savers that run along with some minimized high-powered applications such as PowerPoint or Excel. Usually, the animated part of the screen saver will disappear. Deactivating the screen saver will often cause all the icons to turn into white squares, or parts of the desktop to disappear. This is caused by the GDI heap losing all data about the attributes of each icon. With resource-heap overflows, the only surefire cure is to quit trying to do so many things at once, or to upgrade to Windows 9x, Windows NT, or Windows 2000 which do not have resource heaps limited to 64 KB each. In this case, the addition of RAM (the usual cure for not being able to run all the programs you want at the same time) will not help. Remember, RAM is only one of the computer's resources.
Application-specific errors are frustrating because there is nothing you can do to make them go away. In order to fix these errors, the application software must be repaired at the source. When these errors occur, contact the company that makes that software-often there is a "patch" (which can usually be downloaded from the company's Web site) available to repair the problem.
If a GPF is created by bad RAM, it will occur over and over again at a specific memory address. You will be able to detect this by writing down the exact message on the GPF screen. If the address noted in the message is the same, time after time, you can suspect bad RAM.
When the computer begins to act strangely, this is known as "erratic behavior." Video cards are notorious for erratic behavior that can be as innocuous as colored dots on the screen (wherever the mouse has been moved) to the occasional glitch after installing the latest video driver.
Printer drivers can create problems by causing the printer to spew forth nonsense characters that bear no resemblance to the original text or graphic image.
To resolve these problems, you must first identify the problem driver. For video drivers, go into the Control Panel and select the Microsoft VGA driver. It is very slow but will cause no problems. After the driver has been identified, go online (either through the Internet or directly with the company) and verify that you are using the latest version for your particular device. Also check for an odd setting in the .INI file that goes with the driver. The .INI file will share the same name as the driver, but not all drivers have .INI files.