So your KSP is crashing?
Most crashes are caused by running out of memory. You can confirm this by finding your error.log file and looking for the line that starts with "system commit total/limit/peak." If the last number is close to the middle number, you likely ran out of memory.
Your operating system will use free space on your hard drive for virtual memory. This is called the pagefile or swapfile. If the hard drive where your pagefile is located is nearly full, allocations will fail and the game will crash. Usually this is the drive where your operating system is installed - it does not matter where KSP is. If your drive is nearly full, get wiztree to identify what's taking up the space and delete it or move it to a different drive. As a last resort, you can move the pagefile to another drive with more space, but note that you always want your pagefile to be on your fastest drive or it will severely slow down your system.
By default windows will limit the virtual memory amount to 3x your physical ram size. If you only have 8gb or less of physical RAM, then the pagefile might be limited even though you have lots of free space on your drive. You can manually increase the pagefile size in this case (be sure to set it to at least 3x your physical RAM size). But excessive use of the pagefile will be slow and you should think about upgrading your RAM.
Closing other memory-hungry programs like steam, chrome, discord, etc will keep more virtual memory available for KSP.
Decreasing the texture resolution setting in KSP is an easy way to reduce the memory that it uses, but obviously it makes the game less pretty. You can change this with the TEXTURE_QUALITY entry in the settings.cfg file in the root ksp directory. 0 is max quality, and each increment cuts the texture resolution in half (1 is half quality, 2 is one quarter, 3 is one eighth, etc).