My computer is currently running windows XP on a LAN Network. I'd like to use linux but I want to hide myself. I don't want to be the only linux system on a network full of windows XP computers. Is there something I can do? While browsing the internet I understand that I override the user agent (The server runs a squid caching proxy). But otherwise how do i disguise my self as windows xp computer on the network? Im running Windows XP dual boot with Macpup linux. I don't want to trigger of the admins. I just prefer linux. A simple explanation would help a lot :P
First, I'm afraid I find myself seriously questioning your motivation: why do you want to hide what OS you're using from your LAN ? To me, it sounds like you're trying to work around the requirement from your IT department which is a bad idea, professionally speaking.
Second, what you're asking is technically difficult. You can mimic many of the properties of a Windows machine but getting it 100% right is going to be difficult. Furthermore, there are some functionalities that simply cannot be duplicated because there is no equivalent in Linux (remote registry access, for instance, or most of the RCP servers implemented by a Windows client). There is also the fact that even at the IP stack level, Windows and linux behave differently by default and tools like nmap will have little trouble identifying your machine as a very peculiar windows XP indeed.
I cannot condone lawless activities such as disguising your system so as to evade the rightful gaze of your legitimate system administrators. Therefore I will speak here only in a theoretical way, for the sake of Science.
There are a wide number of ways that the operating system of a given machine can be detected from the outside. In particular, nmap includes an option for "OS fingerprinting" which works by looking at the specific way IP packets are sent, and reacted to, by the OS. This is outside the realm of the user configurable. The bottom-line is that if the sysadmins are at least half thorough in their surveillance, then they will detect a Linux system as such.
So the only real way to make your OS "look like" a Windows is to involve a real Windows OS. You could use Linux in a VM, with Windows as main OS for the computer and giving network access to the Linux system through some NAT or with an applicative-level proxy (e.g. a Web proxy). It is also possible to reverse the setup and have Linux as main OS, and Windows in the VM -- but still making all traffic go through the Windows. That one is a bit more complex and it will require your virtualization solution to do some kind of bridging between the physical network interface, and what the Windows-in-VM sees. But it is doable. If using VirtualBox for VM, make sure to read section 6 of the manual.
Most IT admin tools perform specialized port scans to query various ports of a machine to determine the OS. You would need custom services on all the ports a normal WinXP machine uses and scripts running to respond with pre-configured values. There might be software out there to do that, but as this question is not appropriate for this site, I'll leave that investigation to you.