Chances are the pc is wanting to increase the pagefile.sys size and the harddrive might not have enough space.
Automatic pagefile size with invariably be 1.5 times the installed memory size.
Whilst people with 4g+ often remove the pagefile altogether, I tend to keep one and make it 8g for 4g installed.
Best method for installing new memory:
1. Be sure the harddrive (c:\) has plenty of free space. Using 4g installed memory as an example, the bare minimum needs to be 8g+5g free on the drive, or partition - obviousy if u have loads more, ur laughing. (the 5g is for things like Nero if the user wants to make a DVD)
(be logged in as administrator)
2. Before physically installing the new memory, turn the pagefile completely off, on all drives/partitions.
3. After restarting the pc, make sure the old pagefile has been deleted. Turn on the necessary folder options so u can see system and hidden files - to be sure. If the file is still there, delete it. If u can't delete it, ur not the admin.
4. Install the new memory, being sure u comply with the mobos channel operation.
5. defrag the drive, preferably with something like AusLogics Disk defrag. XP's defragger should be ok tho, it will atleast give u a graphical representation, where ur ideally looking for no green blocks and all the blue stuff nicely stacked together. ***
6. Set the new pagefile to custom and 2x the size of the physical memory. One partition is enough.
Now u should have a newly created pagefile.sys, and better still it'll be unfragmented forever.
*** u can check after setting the new pagefile that it's unfragmented by seeing if there is a large single green block.