Links

A-Squared Free Anti-malware program.
Grisoft AVG Free Excellent antivirus software.
HijackThis Anti-malware program. Especially useful for removing unwanted browser extensions.
IZArc Compresses and extracts files in many formats including Zip.
MemTest86+ Utility for diagnosing memory problems. Faulty memory can cause intermittent crashes and errors that are very difficult to trace. Use MemTest86+ to ensure that your computer's memory is working perfectly.
SpeedFan Monitors system temperatures and, if possible, reduces noise by slowing down fans.
SyncBack Free The perfect solution for backing up important data. SyncBack is very fast because it only copies files that have changed since the previous backup.
Windows Defender Anti-malware program by Microsoft.
Xenu's Link Sleuth Searches any web site for broken links. Extremely fast.

Connected: An Internet Encyclopedia Technical articles describing how the Internet works.
Definitive BIOS Optimisation Guide Comprehensive guide to BIOS settings
W3 Schools Free tutorials on all aspects of web design, including HTML, XML & CSS.