I’ve written about DB2 9.7 install issues, such as here and here, but neglected to record one that bugged a co-worker today.  You log into Windows after installing and are greeted by a popup message:

SQL5005C System Error. A system error, probably an I/O error, was encountered while accessing a configuration file.

It typically comes from DB2 First Steps (db2fs.exe), but that may not be obvious.

The likely cause is that you enabled DB2’s extended Windows system security (the new default), but did not add your user ID to the DB2ADMNS or DB2USERS group.  The DB2 installation program tells us to do that, but if you didn’t do the install, you may have never seen that advice.

Just add your ID to the group and problem solved.  And maybe turn off the db2fs auto-start so it doesn’t annoy you each time.