Win 7 LAN access problem

Sounds like you had associated the shortcuts with Windows Media Player. Take a look at your file associations.
Control Panel\All Control Panel Items\Default Programs\Set Associations

hi,did you try right click on the non media file and choosing open with ,and choose the program that should be opening them

Right-click on any device and I get 'Open with Media Player'. On the Aspire 1 it does show the WD drive as a separate item in 'Computers' but only 1 shared file is available. Files on the local computers are normal until you try to access them from the LAN!

Just to clarify, all machines are running win 7, (a mix of Starter, Home Premium and Pro) but are not set as a 'Homegroup'
Took the Netbook home and it connected normally to my (XP) network. I did wonder if malware was involved but various scans were clear. I also ran System File Check on the portables with no change.

If I understand you correctly you have multiple PCs that are all showing the same, "Open with Media Player", but when one is removed and attached to another workgroup it shows up okay. Since they all have the LAN in common. I know what I suggest is crazy but what I would try is to shut the workgroup down then recreate it from scratch as a starter.

My laptop gets connected in other lines in the network, but does not get in my room's router, again others laptop gets connected in my room's router. When I contacted one person related to the network administration, he answered me to change my OS either to Windows XP or Vista.

Now I'm connected in the same network in another router.