Can't Access Win7 shares from Axim PDA

Hi
This is my first post. I am hoping someone can help. I have 4 PCs linked by a wired LAN. I also have a Dell Axim X51v PDA, which I use to listen to music files from a music collection on PC1 via a wireless access point. All was working fine under XP, but now that I have upgraded PC1 & PC2 to Windows 7 Ultimate 7600, I can no longer access shares on those machines using the PDA. I can see the PC's using the network plugin, or Resco Explorer, on the PDA, but when I try to expand them to see the shares I get nothing. The XP PC's shares still work fine, and I can ping the Win7 PC's with the PDA.
I can access the internet with the PDA
I have tried with and without Windows firewall, and I have tried setting LMCompatibilityLevel to 1, as suggested in another post.
The XP machines can access the Win7 shares OK, and vice versa.
I have tried going back to the original Windows Mobile 5.0 on the PDA, (I normally run WM6.5), but I still get the same results.
I am not using any encription on the PDA at this stage, and the Win7 shares have read/write permissions for everyone.
I feel that there is some security setting on the Win7 machines that I am missing, but for all my searching on the net I can't seem to find it.
Hoping someone can help, because apart from this snag there is a lot to like about Windows 7

You will need to install the Windows 7 Mobile Device Center in order for your device to share files with Windows 7. This download, once set up correctly, should enable you to see the device and share files with it.

Windows Mobile Device Center 6.1 | Windows Vista Support

Thanks for the reply.

I have Windows Mobile Device Center installed (Win7's replacement for XP's Activesync), and that is working fine, and allows me to syncronize/transfer files when the Axim is connected to the Win7 PC via the USB cradle.
What I am having trouble with is accessing the Win7 shares wirelessly over the network, which is something I could always do , and still can on PC's running XP