This is just a wild guess but will it work if you enclose the command and it's switched in quotes ...

try :

Code:
$hotfixexe="'c:\test\ms04-020\Windows2000-KB841872-x86-ENU.exe"
$switches=" /quiet'"
? $hotfixexe + $switches

run "runas.exe /user:%COMPUTERNAME%\admin " + $hotfixexe + $switches
sleep 1
sendkeys ("password{ENTER}")

quit
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