The Color LaserWriter 12/600 PS printer software for Windows 3.1x installs VECPD.386, a bidirectional parallel port driver that was not intended for Windows 95. If you upgrade to Windows 95, or install the Windows 3.1 printer software after installing Windows 95 the VECPD.386 file is installed. This file prevents the computer from being able to access the printer port properly. To prevent VECPD.386 from loading, remove the following line from the [386 enh] section of SYSTEM.INI and restart your computer:
device=vecpd.386