you have 5.00m33-6?
when in XMB press 'SELECT'
switch the 'USB Device' to 'UMD Disc'
connect your USB cabe
and simply drag & drop the .iso file to your PC

for further compression to the .CSO format and so on i use
UMDgen.
Using the Memorystick also preserves Battery life so you can fight those nasty aliens even longer.