For the connoisseurs: memory allocation in Windows VS caching?

Question

Windows

Situation: A computer with 4 GB of RAM, running Windows 7 64-bit, was engaged in a complex task for several hours (importing a large data array into SQL from a bunch of small files (100.000+ files)). Gradually, the computer slowed down more and more and it became almost completely unresponsive. The Resource Monitor on the Memory tab under Physical Memory shows:
Reserved Hardware: 2 MB
Used: 3874 MB Changed
: 1 MB
Standby: 163 MB
Free: 46 MB
down side)
BUT! If you sum up the processes by the values ​​in the Completed (KB) or Working Set (KB) column (can anyone explain in a nutshell what is the difference between these values?), then by sum it turns out that all processes consume not more than 2 GB of memory.
Question: who ate almost 2 GB more memory and why is it not freed up? (no time-consuming or memory-intensive tasks are currently running).
PS In the task manager on the "Performance" tab, this is the memory picture:
Total: 4094
Cached: 178
Available: 211
Free: 34
Kernel memory:
paged: 361
nonpaged: 66
System:
handles: 43735
Threads: 1587
Processes: 126
Allocated (MB): 5979 / 8187 (I wish someone could also comment on what these numbers mean)
I'm only hoping for the experts.

Answer 1

>>Free: 46 MB
This is the amount of actual free memory, ie. not involved at all. Under normal conditions, it should be slightly free, because. the rest of _available_ memory should go to caching.
>> what is the difference between these values
​​Well, in general, if you hover your mouse over the headers, then a tooltip pops up there;)
Completed - how much virtual memory is allocated to the process (i.e. for example, the process asked for 2GB to allocate - it will show 2GB here);
Working set - how much is currently in RAM, i.e. the value can be less than "Completed".
Here's a good example:

>>Question: who ate almost 2 more GB of memory and why isn't it freed up?
Well, where exactly she went only by the final indicators is difficult to say, for more or less specific fortune-telling, at least screenshots are needed. It is highly desirable to take Process Monitor (www.sysinternals.com).
>>Total: 4094
This is the amount of _RAM_ (without swap)
>>Cached: 178
This is the amount of RAM allocated for file caching
>>Available: 211
This is the amount of RAM that the system can allocate to the process (consists of cache+free)
>> Allocated (MB): 5979 / 8187
Memory allocated - 5979 megabytes out of the maximum available 8187 megabytes, consisting of ~4096 MB of RAM and 4096 MB of the swap file.
Which, by the way, indirectly indicates that someone ate a lot of memory, as much as 1.5 times more than RAM.