Network connection problem with a computer running on XP

My computer is running XP (SP3) and I’ve been experiencing some connection problems for almost 2 days now. This computer is part of my network. The internet connection does not reach the map drive of the server. I’ve tried shutting down the unit , restarting it again and running the virus scan. I’ve also checked if I need to defrag , since it says “low disk space” even if there is still over 100GB free space. I’ve already checked the firewall and reset the router, but still, nothing happens. I don’t know what to do with this. Please help me fix this problem.
