C&C 95 should be pretty smooth on 233mhz mmx. The slowest PC I have that will run C&C95 well is my 266mhz Cyrix MediaGX witch is basically a 486 "DX8" with MMX and no L2 cache . It runs the game well enough but I do get occasional slow-downs witch seem to be related to loading bits of sound or graphics, involving explosions mostly.
It's possible you have a driver issue, either related to the sound hardware, video card or direct X. Have you tried un-checking the "Back buffer into video memory" box in cncsetup?
As an experiment I'll slow down my K6-2+ to 200Mhz and have a go at the game under win9x. I suspect it will run fine tough.
Ok I just run C&C95 after setting my K6-2+ to 200Mhz via setmul and it was smooth as silk. I loaded up a savegame of GDI mission 10 witch is pretty action packed from the get go and played for about 10 minutes. Had the game set to it's fastest speed and units were zooming about the map, had to slow the game and scroll speeds down. The only time I did encounter any kind of issue @ 200Mhz was when the music track changed - and I'm not running the game with the CD - I'm running it entirely off the hard drive. When loading a new music track the game will freeze for a millisecond. Other then that it ran perfectly smooth.
That means there's something wrong with your setup. It might actually be a good idea to check your system with a utility like AIDA32 under windows and see if everything is setup correctly - FSB to 66, the correct multiplier, memory timings and so on.
Now time for silly questions - What kind of cooler are you running on your pentium 233? Is it running on a dual voltage socket 7 motherboard? Are your timings set correctly in BIOS? Is the l2 cache detected correctly? Are CPU to PCI writes enabled in BIOS? Is "assign IRQ to VGA" enabled? Are you running win95 or 98? How much ram do you have installed and how much l2 cache? What sound card and driver is in the system?
I also discovered an interesting tid-bit. The K6-2's really can't do 2x multi. It seems when you select 2X via setmul it doesn't actually drop the multiplier to 2X, but instead sets the FSB to 80MHz and the multi to 2.5.... too bad it can't set the FSB to 66 or lower.