http://m0n0.ch/wall/

I just installed this on an old dell I had lying around, so far it seems really good.

but... everything seems to be going a bit slower, games ping times are really high, and even web pages are loading slower.

Anyone got any pointers?

How old is that dell (CPU, NICs)?
What rules do you have defined on that fw?
How is your network set up?

The Dell has a Pentium 1 at 266 and 64mb of ram. should be enough to run it at a proper speed.
The Nics are a new realtec one and one that came with it. not sure what kind it is and it only runs at 10mb/s.
Not setup many rules yet, except the traffic shaper(Flatmate leaves torrents running 24/7 and this program is the perfect soltion!) I set P2P software at lowest priority and share the bandwith evenly.

Network is setup like:

Internet-->ASDL modem-->[Dell old NIC--M0n0wall--Dell realtec NIC]-->HUB-->2 PCs running XP

Did that make sence?

Well, the obvios solution would be to eliminate components one by one and see what causes the lag.

Disable any software firewall on the XP machine(s). They can introduce great lag sometimes.

First ping the other computer on your local network. Any packet loss?
Ping the Dells internal interface. Packet loss?
Ping Dells external interface? Packet loss? Response time?
Ping a server on the ISPs network (the gateway seen by Dells external interface for example). Response time, packet loss.
Disable traffic shaping. Ping..
Disable packet filtering. Ping..
Remove the Dell machine completely. Ping..

As you can see the ping command is your friend