Cheat:

  Save your game, and note how many credits you have.

     Open  up  the  savegame  in an hex editor (the first save game is
named  X0.SAV  then  X1.SAV etc etc) DO NOT try and edit X99.SAV, it's
the save game list.

     Open  up  windows  calculator, switch to scientific view. type in
your  credits *withouth the comma* ie. if you have 298.35 credits, you
type in 29835 and click Hex.

     It  will  give  you the value of 12A, since in hex each number is
represented  by  2  digits, simply put a zero at the start so it makes
012A.

     Now search for this value in the savegame. You will find it twice
and  you  must  change  it  in both places. The first location is near
BC90, although this *can* change...

     To  reiterate,  convert  the  whole  number  *without* the comma.
change both places!