Its because, there isn't one. Intel GM-45 chipset has no drivers for windows 7. check here for yourself..
*downloadcenter.intel.com/SearchResult.aspx?lang=eng&ProductFamily=Embedded+Components+and+Flash+Memory&ProductLine=Embedded+Chipsets&ProductProduct=Mobile+Intel%C2%AE+GM45+Express+Chipset+%28embedded%29&ProdId=3032&LineId=1705&FamilyId=44
Your best bet would be updating it with drivers by windows. Try selecting "search drivers online" or something like that in your 7.