#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(?m).*totaldisksize="(\d+(?:,\d+)*)".*"
Local $sString = "<drives name="drive 1" deviceid="\\.\PHYSICALDRIVE0" interface="SCSI" totaldisksize="136,7">" & @CRLF & _
"<drives name="drive 1" deviceid="\\.\PHYSICALDRIVE0" interface="SCSI" totaldisksize="1367">"
Local $sSubst = "$1"
Local $sResult = StringRegExpReplace($sString, $sRegex, $sSubst)
MsgBox($MB_SYSTEMMODAL, "Result", $sResult)
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for AutoIt, please visit: https://www.autoitscript.com/autoit3/docs/functions/StringRegExp.htm