One of my first computers was a ICL 486 SX25 computer with 4mb of ram. I wanted the DX25 chip but was told there was a six month waiting list for that. The DX had a maths co-processer which made any calculations quicker. I wrote a word document of about 100 pages and it couldn't process that but kept crashing. I got around that by printing the document in batches of twenty pages. I went out and brought a 16mb Ram chip and also a 540mb hard drive to replace my 85mb hard drive on the PC. I always remember the price I paid was £486.
I got home a took out the old drive after backing up with twenty odd 1.4mb floppy disks. Moved the 4gb ram to another slot and put the new 16gb ram in the first slot. and removed the old hard drive and replaced with the 540mb drive. This took over an hour to put it all back together. Switched on and it didn't boot up because of a problem. I wasn't very happy. At the time there was some problem with memory chips not matching so you had to put them in different slots that weren't connected. Open up the PC and removed the 4mb and put it all back together again. It still wouldn't boot up!
Took computer apart again, removed 16mb chip and replaced with the 4mb and put it all back together again. Booted up and it worked. The new 16gb chip was faulty. Thinking back to when I brought it I remember the salesman pausing before giving me the chip. I reckon he knew the chip was faulty but sold it to me anyway. I had brought the chip at the computer fare at the NEC. The firm had it's shop in Wolverhampton and it took me over an hour to reach it and exchange it. I expected some trouble but they exchanged it with no arguments. Went back home, took the PC apart again, refitted the new ram and put the 4gb ram in another slot then, put it all back together again. Switched on and it worked. I had 20gb ram and the 540gb hard disk. I never used that firm again. I then printed that Word file and it did it all in about five minutes no problem.
On a PC you can see how much memory a process is using and the size of the page file. The page file outputs to the disk but can be anywhere where there is free space. This puts a heavy load on the disk as it keeps spinning to use up spare space on the disk. Creating a virtual drive uses space that is next to each other so speeding up the page file usage. It locks this memory block so other programs can't use it.