reboot.exe is used for computers with SiS graphics. The same file loads from the exact same location on the systems here in work that use SiS onboard graphics. I assume that offboard SiS graphics card would do the same thing, but I could be wrong.
What graphics card does your friend have in his machine?
excoelis: are you using DHCP or Static for the IP addressing on your router? If repairing IE or using Mozilla (yuk - we wont continue on that conversation) doesnt fix the problem, then try Static IP addressing (if you use DHCP (Dynamic IP) addressing) by setting
IP: 192.168.1.100
Subnet: 255.255.255.0
Gateway: 192.168.1.1
Primary DNS: 192.168.1.1
Also, in the WINS tab, check "Enable NetBIOS over TCP/IP". I use that setup (different IP though) at home using a linksys router. A mate of mine has had troubles with routers and DHCP, I changed his IP to static and it stopped causing problems.