WinXP not staying logged into network resources

I have one specific computer that I need to back up separately to an Iomega NAS drive. We have matching login account, no password as the item is sitting in the same locked office but on the network.

The problem is, every time we reboot, it needs to log into the NAS manually by clicking on the network resource, however, the backup runs at night and simply does not see that drive anymore – we have the drive letter automatically mapped as well.

So why do we no longer have access to it rebooting and no longer after a long period of time? We checked to make sure the computer is not sleeping nor hibernating. I’m not sure if the problem is specific to this computer or whether it is an Iomega issue.

Any thoughts?