If space is limited and you have dual boot or a multiboot environment, you can share the same pagefile.sys. Windows 9x, Windows NT, and Windows 2000 all use the same registry value to tell the operating system which file to use as a pagefile and what its opening and largest values are. The syntax is the same. You don't have to have them set to the same size but its probably safer to do so. Each operating system will open the file and create any structures it needs at boot time. For Windows NT:

Hive: HKEY_LOCAL_MACHINE
Key: System\CurrentControlSet\Control\Session Manager\Memory Management
Name: PagingFiles
Type: REG_MULTI_SZ
Value: c:\pagefile.sys 256 512

This example uses c:\pagefile.sys with an initial size of 256MB and a maximum size of 512MB. For Win9x, edit the system.ini and using the following syntax in the [386Enh] section:

PagingFile=C:\pagefile.sys
PagingDrive=C:
MinPagingFileSize=256
MaxPagingFileSize=512

explicit advice on how to get various combinations of systems to coexist