|"i have currently formatted one PC on the network"|
A FORMAT is a process of preparing a drive for use. Either a new blank drive, or to wipe an existing drive.
One presumes here you mean you have done a fresh install of the operating system and that PC is no longer able to access your LAN.
There can be a number of reasons for this and you have not given any useful information in order to determine where your problem might be.
You say that other systems cannot ping this one. Can the "formatted" system access LAN resources? Can it ping anything? If it can then it is probably a firewall issue.
If it cannot establish a connection then you should start with NIC drivers
Goin' Fishin' (Some day)