Port drivers are loaded either at boot time or upon demand, depending on the version of Windows and whether the port driver is plug-and-play compliant.
Port drivers that do not comply with plug-and-play are loaded statically at boot time. (The same is true for all port drivers under versions of Windows prior to Windows 95.) In such cases, the port driver must have an entry in the [386Enh] section of the SYSTEM.INI file. With Windows 95, this section causes a device node to be created. Static port drivers are unloaded only when Windows 95 exits.
Windows 95 loads plug-and-play port drivers when a VCOMM client attempts to open a port that the driver supports. Plug-and-play port drivers are unloaded when all ports supported by the driver are closed.