XP LAN access problem.

Recently for no apparent reason internet access from xp pro was lost even though it was connected. The Chrome browser suggested a fix which I followed, something in security, I think, this restored access. Since this event I have been unable to access a Nexus 7 13 tablet through USB or WiFi. Windows explorer sees the Nexus tablet when connected by usb but no files on it. Likewise ES file explorer sees the xp machine over wifi but no files on it.
Not knowing anything about communication protocols any help in getting this working again will be greatly appreciated.
Thanks, John.
Thanks for the reply. I will need time to digest that info. The last android update which occurred in the same time frame seems to have set the usb use to charge only, once set to file transfer the PC to nexus 7 data transfers work. Now to figure out why the wifi connection does not work.
WiFi was working all along, I discovered that the remedy to loosing internet connection on the xp machine also set all the file shares to read only so copying to the PC failed.