Been doing that for a long time. It did not help speed up my ageing Acer notebook. Here is the procedure to change pagefile size:
Click the Start button,
right-click Computer,
and then click Properties.
In the left pane, click Advanced system settings.
Administrator permission required If you’re prompted
for an administrator password or confirmation,
type the password or provide confirmation.
On the Advanced tab, under Performance, click Settings.
Click the Advanced tab, and then, under Virtual memory,
click Change.
Clear the Automatically manage paging file size for all
drives check box.
Under Drive [Volume Label], click the drive that
contains the paging file you want to change.
Click Custom size, type a new size in megabytes in the
Initial size (MB) or Maximum size (MB) box, click Set,
and then click OK. Recommend 4096 / 8192 or more depending on size of hard disk & physical memory.