SVCHOST contacted from remote machine

Hi,
I just reinstalled my computer (Win XP) and have this warning popping up in my sygate firewall every few minutes:

"generic host process for win32 services (svchost) is being contacted from a remote machine using local port 135 EPMAP location service dynamically assign ports for RPC do you want to allow this program to access the network"

Before the last re-installation, I allowed it once, after which a file called tftp.exe tried to connect to a remote site 3 times a minute, and sometimes my computer would count down to a restart (as Blaster did).

I reinstalled XP again (Total reinstall),
I downloaded the Microsoft security patches, installed norton antivirus and sygate firewall. But still i'm bothered by this 'remote machine trying to access the network.'
Is it a thing to worry about, what causes it, and how to stop this..?

Thanks for your help,
Jarra

This link will help: http://isc.sans.org//port_details.php?port=135&isc=028cb1441d87f69c476b63671084fa0b

Read the various comment. Many viruses/worms will use Port 135 to connect, so it is a good thing to have this port blocked from the outside. Change your notification in your firewall, etc. so it does NOT notify you whenever a connection is made from the outside.