Mine is a single-user Win98SE machine yet Windows insists on me having an username (PWL file). Now a mysterious new user seems to have emerged, calls himself RNA.PWL. I have this feeling that 'RNA' means something in particular but I can't think what it is.

I delete RNA.PWL regularly but it keeps coming back!

Anyone have any insight into this phenomenon?

The file RNA.PWL is supposed to countain your dial-up password. If you don't use dial-up then, you must have installed some dial-up update.
Nothing to worry about in this case...

if you save your passwords, they are stored in a PWL file. if you don't save your passwords, no PWL file will be created. read these MS articles:
http://support.microsoft.com/kb/148925
http://support.microsoft.com/kb/152104
http://support.microsoft.com/kb/140709