Install /a (administrator). Then download the administrator versions of the files and integrate:
msiexec /a g:off2kdata1.msi /p g:data1.msp SHORTFILENAMES=TRUE /qb+ /L c:tempdata1.txt
msiexec /a g:off2kdata1.msi /p g:sp2admin.msp SHORTFILENAMES=TRUE /qb+ /L c:tempsp2admin.txt
Where
g:off2k is the administratative install point
data1.msp the 146 MB administrative SR-1a update file and
sp2admin.msp the 29 MB administrative update file for SP2
data1.txt and sp2admin.txt are logfiles
The same way you can integrate all later updates as well. Burn the whole project to a CD to install from