There really is no good reason for an IRC client to be bulky. It should be very small, lightweight and run very fast. While there are a few good IRC clients for Windows, my personal pick is XChat 2 for Windows, a free Windows version of the popular XChat software.
For those of you who bounce between Windows and Linux environments, you probably already use XChat on Linux. If so, XChat 2 will be very familiar to you.
The PCMech.com weekly newsletter has been running strong for over 8 years. Sign up to get tech news, updates and exclusive content - right in your inbox. Also get (several) free gifts.