Uhh I'm going to have to recommend against doing what Putty says unless you really know what you're doing.
Disabling AV, firewall and other important programs is generally not a good idea and if your on a direct connection to the internet could cause a substantial security risk to your system.
In addition to this I can't see firewall and AV adding anything substantial to your ping.
You want to make sure no other programs are running which are using your internet while playing SA:MP such as p2p software or downloads. These substantially increase your ping. If this doesn't make a difference, there's not much you can do other than move to a better ISP.
For more information have a look at
http://en.wikipedia.org/wiki/Lag, specifically at the Latency section.