The Watcom download is about 45 MB. It took 2 hours to download on my connection (56K, actual 46600). The IDE is very straightforward, but the assembler looks a lot like GAS and I'm not happy about that. But Watcom does come with a DOS extender (used to be DOS4GW) and used to be what was used by the industry to create old DOS protected mode games. I cannot tell you how many programs used DOS4GW as a DOS extender back in the day. I'm assuming since they used this extender, they were also using Watcom C for their code.
I do not remember the URL and cannot find it in my Favorites section. Look up Watcom C/C++ on www.excite.com or www.google.com and it should show up near the top of the list.
Other topics that may lead you to the compiler are 32-bit protected mode, DOS extenders, flat-real mode, and 16-bit protected mode. You will also find some code from www.intel.com for placing the processor into protected mode and their is a site that shows you how to alter the GDT selector limits to be able to access 4GB but be in real mode (flat-real mode). May not be the best solution, though.