D2KWUTIL is an add-on for forms on MS Windows. It adds a number of useful utilities, such as a file open/save box and the ability to read or write to the registry. There are plenty of other tools in there as well and there may be something you can use to get the drive serial number.
The version currently downloadable from OTN is for Forms 6i, but you may be able find an older version for 4.5.
If you could upgrade to forms 6i you could use the version from OTN directly.