Fresh install of LCPDFR? And if you wouldn't mind attaching your GTA IV directory
1] GO TO GTA IV MAIN FOLDER
2]CREATE A SHORTCUT OF YOUR LAUNCHGTAIV APPLICATION
3]GO TO PROPERTIES OF THE SHORTCUT
4]THEN GO TO THE SHORTCUT TAB ON THE PROPERTIES
5]IN THE TARGET BOX AFTER THE LAST " PUT A SPACE AND TYPE -AVAILABLEVIDMEM
6]RIGHT CLICK YOUR DESKTOP BACKGROUND AND GO DOWN TO SCREN RESOLUTION AND CLICK IT
7]CLICK THE SMALL BLUE TEXT THAT SAYS 'ADVANCED SETTINGS'
8]NOW JUST CHECK YOUR DEDICATED VIDEO MEMORY
NOW BACK TO THE GTA IV PROPERTIES SHORTCUT PORTION:
9]TYPE IN THE NUMBER OF YOUR DEDICATED MEMORY AFTER
-AVAILABLEVIDMEM
10]NOW CLICK APPLY
11]CLICK OK AND START UP YOUR GAME AS 'RUN AS ADMINISTRATOR'
12]ONCE AT THE MAIN MENU WHERE YOU CHANGE YOUR OPTIONS, GO TO GRAPHICS, AND AT THE BOTTOM YOUR NEW VIDEO MEMORY USAGE SHOULD BE THERE
13]NOW JUST ADJUST YOUR GRAPHICS WITHIN YOUR SELF GIVEN RANGE AND START YOUR GAME, IT SHOULD WORK
Try this as well