Hi Eric,
Welcome to the Digital Signage Portal. We hope that our member will be able to provide you with some guidance and help with your project.
From my point of view, Powerpoint has been the traditional tool for displaying content on a screen and but is quite limited in it's capabilities.
There are several options you may want to consider:
1. Keep using powerpoint - however there is no easy way of scheduling content to be displayed on certain days or events. You can use certain tools or even the Microsoft Task scheduler to open up a powerpoint presentation at a particular time. Have a read of this article from Microsoft
http://support.microsoft.com/kb/308569The only issue I see with this is that its not the most effective and professional way of doing things and it may deter the client to no longer use digital signage if the experience is bad.
You may have to tweak the Powerpoint settings etc so that the presentation loads in full screen and so that it doesn't load the microsoft powerpoint splash screen.
2. Use a digital signage player (this is a hardware and software package) - although it comes with a cost, your client will have the benefits of scheduling different types of content on the day. Eg play flash, video, rss feed etc.
3. To reduce costs you may already have the PC and all you need is the software. There are a quite a number of software packages in the market and some may be free or some have a 30 day trial or negotiate this with the software vendor. As you mentioned if the client to try it and if they like it they can buy it.
Hope this helps.
4.