While Initializing Device IOS and I/O Subsystem driver failed to load

[suresh annamalai]

Recently, I upgraded 128mb RAM memory (now total of 256
mb). If computer used 128mb ram no error displays. If it
is uses 256mb ram it gives the error

While Initializing Device IOS:
Error: An I/O subsystem driver failed to load
Either a file in the ./iosubsys subdirectory is corrupt
or the system is low on memory.

After step-by-step load process. I inactive the following
files it is works (c:\windows\system\vrtwd.386 and
c:\program files\symantec\symevnt.386)

Currently I removed the entries in registry to avoid
window start error message.
Any body give me a suggestion what is these two file
doing and how to prevent this error.

thanks in advance