You might try using this simple method which I first posted in another thread and regarding a different subject. It might do what you want.
For anyone who wants to see the contents of their sd card on their PC and be able to copy/transfer files from one to the other, why not give this a try, it is very simple and works for my A500.
Before you start you need your A500 to be rooted and you need "USB Mount All version 1.3" from the Market cost $1.99
(1) Have your PC switched on, don't connect your A500 yet but switch the A500 on.
(2) Run USB Mount All and you will see your sd card as a "Device" named "ext_sdcard".
(3) Press the tab "Mount" next to your ext_sdcard. You will see two messages "Mount has been granted Superuser permission" and "Device successfully mounted".
(4) Press the "Menu" tab in the top Right hand corner of the screen, this opens a small box entitled "Settings". Press on "Settings" and you get 3 options, make certain all 3 options are ticked, ticking them if they are not. (The important thing is to have "Mount on Bootup" ticked"). Press the Back Arrow twice to get back to Home Page or where ever you started from.
(5) Re-boot the A500 and after it is back running connect it to your PC using mini usb connector.
(6) Now check your PC and open Windows Explorer, you will find under your A500 Device most of the folder/directories that are in /mnt/sdcard (which isn't all that relevent to this) BUT importantly you will find a folder/directory entitled "ext_sdcard" which for those of you who noticed is the exact name that "USB Mount All" called your sd card.
(7) Now use Windows Explorer to copy and paste whatever you want into the "ext_sdcard" folder.
(8) Please note that when you start to copy files you will get up a warning box stating "Do you want to copy XXXXX to your device?". You are given 2 choices (1) No skip this file or (2) Yes.
(9) Put a tick in the box at the bottom Left and click on "Yes".
(10) When finished safely disconnect your A500 from your PC and re-boot your A500.
(11) After re-boot go back into "USB Mount All", chose top Right menu and settings box and remove the tick from the 3rd option "Mount on Bootup". Each time you are going to copy, move or delete files first of all put the tick back in the 3rd box and when you're done take it out.
Your Done. If you use any File Explorer to look at /mnt/external_sd you will see all the files residing on your sd card including those you've just copied.