The Date/Time box needs to be checked as for without it checked its greyed out - disabled, then click on apply to save this change.
Unfortunately I have not used this feature before to help with placement on the powerpoint, but I would think that it should allow for you to place it where you want it as a normal object similar to how a text box or image can be moved.
I also dont have Office 2007 or PowerPoint 2007 to be able to play around with it at my end. The last version of Office I bought was 2003 and since then I moved over to Open Office and then Libre Office which are free and plenty of features and cross file compatible with MS Office formats.