You could use secure copy scp(1)
My preference in a case like this would be to install cygwin on the Windows side and use scp from a cygwin terminal on the Windows server, a'la:
scp <filename> <user>@<ip-address-of-centos-server>:<pathname>/<filename>
// However can be as simple as this case if the file were a.txt, you used root,
// placed the file in /home/root, and the address of the centos server were 192.168.2.10
scp a.txt email@example.com:.
I think overall it would be helpful to have cygwin or a similar package allowing Linux commands on the Windows server and definitely having support services such as FTP for instance if you set up an FTP server on the Windows server machine. Also SCP, telnet, or preferably ssh so you can copy and attach from Windows to Linux as well.
At least until you get your server all set up.