Setting Correct SQL Express Folder Permissions

Hi

I have a vm machine running SQL Express. So as to centralise my data, on the host machine I have a folder with all my data. This folder is shared. In the vm machine I have set up mapped to this folder, so it is visible within in. I can add/remove from the folder in explorer so the permissions look okay up to there.

However, when I go into SQL Express and attempt to restore from a backup into a DB, I cannot see the folder in the folder list presented. When I try and force the connection through the mapped drive letter or unc name, the server fails with a you do not have permissions.

From my reading it looks like I have got a network service account set up but, when I look at the logins in SQL Express there doesn't appear to be such an account.

Could someone either
a) point me in the right direction if the netowrk service account is not the way to go
b) tell me how to set up a netowrk service account with the correct privileges to enable me to read /write this mapped folder.

Thanks

Simon