Ať si zaměstnanec nejdřív odviruje PC.

Možná by mohlo pomoct toto, ale nejsem si teď jist, jestli to je i pro Win98?

Click Start, Run and type Command
Type the following and then press Enter after typing each one:

cd\windows
copy regedit.exe regedit.com
start regedit.com [or regedit.com]

Navigate to and select the following key:
HKEY_CLASSES_ROOT\exefile\shell\open\command

Double-click the (Default) value in the right pane.
Delete the current value data, and then type: "%1" %* [with quotes]
(ie., quote-percent-one-quote-space-percent-asterisk.)

Exit the Registry Editor and restart Windows.