You won't be able to connect to your windows pc over the network unless centos is specifically set up for it. Linux uses samba for shares not Microsoft.
It sounds like the connection between windows and centos isn't that stable. Depending on your setup you are either bridging a physical network device to a virtual one or NAT-ing and neither is going to be truly stable on every type of hardware, if some are a bit flakey it doesn't really surprise me to be honest. I would definitely try updating the drivers for your network card as XP 64 bit is not very widely used and it wouldn't be a great stretch of the imagination to think the drivers aren't quite as well tested.
Personally i use winscp (free from
http://winscp.net/eng/index.php) for copying files to and from centos.
Samba can be a total pain to set up for people new to linux but it's one possible option and you could connect to the centos samba share from windows.
http://crazytoon.com/2007/05/22/samb...centos-fedora/