Online Anti-Virus Scanners

Microsoft Live OneCare On-Line Virus Scan

Symantec Online Virus Scan

Trend Micro “HouseCall”  On-Line Virus Scan

Error and Event Troubleshooting

Expert’s Exchange

EventID.et

If all else fails..

DNS Tools

DNSDig

DNSStuff

DNSTools

DNSReport

Microsoft Knowledge Base

How to …

Microsoft Knowledge Base – Basic

Microsoft Knowledge Base – Advanced

Bandwidth Speed Tests

CNet Speed Test

SpeakEasy

SpeedTest.net

RBL, and Mail Relay Testing

MX Toolbox

Network Abuse Clearinghouse

Internet Threats

Internet Storm Center

SenderBase.org

Firewall Port Scanners

GRC

HackerWatch

Audit MyPC

Exchange Mail Test

Subnet Mask Calculator

Cotes.net