connection problem on 1 of 2 PC's on LAN

sorry, i forgot to mention before my previous post that i had reset all TCP/IP settings to default (obtain automatically)
and reset dns to 'obtain automatically'

then later that day, i got more connection problems.

now however (without doing absolutly anything) i have perfect connection again.

this happens frequently on this PC, some nights i can't browse web, other nights it's fine.

i don't think the connection has anything to do with TCP/IP settings as they seem to have no effect.

this problem just seems to come and go (which is why I initially thought it was an ISP problem)