If this error message is true, your fastest recovery
would be to get a DOS UNDELETE program on a
floppy, then
boot the PC from your startup floppy
and put in your UNDELETE floppy, then
C:
cd recycled
A:UNDELETE
and follow the prompts.  The UNDEL app ought
to show you filenames including ?IN.COM
or else eIN.COM.  The UNDEL process writes
the character of your choice (W) in the first place
i.e. changes it back to WIN.COM.  (This is the
way the File Allocation Table works.  Deleting a
file merely changes the first letter of its name to
a special byte that signals free space.)
Then remove floppy and see if the PC will
boot as normal.

If you deleted any other Windows system
file, recovering WIN.COM alone will not cure you.

Creating a New Win.com File When You Cannot Start Windows:
http://support.microsoft.com/?id=136630

How To Extract Original Compressed Windows Files:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;129605