The download is a zip file that contains two versions, testlimit.exe and testlimit64.exe. It is not part of the regular sysinternals tools but is associated with them find it here at the sysinternals site. You can force your system to get more RAM into the 'in use' state easily with the command-line tool testlimit, one of the tools used in the experiments in Windows Internals.

In other words your system is operating as it should be.

(This is not the first choice for finding pages for this purpose, that would be the free and then the zero page list.) Such as when a process hits a page fault that does require reading from disk, new physical page(s) must be allocated to that process, and if necessary these can be taken from the Standby list. It's considered 'available' because Standby pages don't have to be written to disk before they can be assigned to some other use.

page faults to these can be resolved without going to disk) and also for proactive file cacheing by SuperFetch. It's being used as a page cache (it holds pages recently lost from all process working sets i.e. If it helps, Resource Monitor describes all the other RAM as 'Standby'

MIRC 7.74 free instal