Nothing is wrong with your Desktop or Notebook. Your anti-virus or personal firewall might be interfering a bit; if you suspect, disable it.
The main cause? It is called Windows Networking. Basically, all nodes in your Network Neighborhood are participating in a process called Master Election, or something like that. And they are having a hard time/long time achieving that because you are running similar Windows OS, for i.e XP and Vista, XP and 2000 Professional, etc., all of which are client class OS'es. Inject a server OS like 2000/2003/2008 server into your network and that process will be much faster and you'll be less frustrated.
Each node is broadcasting packets using a protocol (not sure NetBios or NetBui or something like that) that operates on top of UDP (a main protocol in current TCP/IP networks). UDP is on top of IP.
If you want to know more about MS networks, I suggest reading docs from SAMBA site at www.samba.org. You'll learn much faster than reading overly verbose pages at microsoft sites. No joke and no bias here!