I don't believe Civ IV/Warlords has significant memory leak issues.
Loading WOTM4 (date unspecified, but BC) takes about 250 megabytes of real memory, and 300 megabytes of virtual memory.
Loading GOTM12 shortly before my domination victory in 1940 something, takes 330 megabytes of real memory, and 420 megabytes of virtual memory.
In either case, Chunky, these numbers are more than enough to push your PC to the edge, depending on whatever else you have open in your process list. The operating system and virus checker alone probably run you at least 250 megabytes more real memory.
Basically, this game demands ram and a properly set pagefile. It's just plain BIG.
Harkonnen's fix dealt with video card memory usage issues that showed up as virtual memory issues. Post Civ IV v1_52, it is no longer necessary.
Buy more RAM. It's good for you.
For example, a pair of 512mb modules,
Kingston ValueRAM 1GB (2 x 512MB) 184-Pin DDR SDRAM DDR 400 (PC 3200) will cost you $99.99 + shipping from Newegg.
At that price, consider getting two.
