No grounded outelsts

We moved to a new house yesterday and my system is still all in boxes. I have to set it up, but am wondering what to do since the house is fifty years old and the outlets are not grounded. Is it safe to connect everything and to fire her up using cheater plugs until we get an electrician to upgrade the system?

Get an outlet tester and try replacing one of the outlets with a new 3-prong one. (Be sure to kill the power first.) You may find that you are safely grounded without having to upgrade the wiring. Worked in my 1948 house.
An easier way to get the same answer would be to use a cheater plug in the existing outlet but ground the cheater plug to the center screw in the outlet cover. All cheater plugs will have either a metal tab with a hole in the center of it or a green ground wire with a connection on the end. Those are designed to be connected to the center screw on the outlet plate, creating a connection to the outlet box, itself, through the outlet cover screw. Testing for that with an outlet tester or multimeter will tell you.

Some outlet boxes are grounded by the metal coax through which the wires run but some older ones are not grounded at all. If you're lucky, your boxes will be grounded and you can either use the grounded cheater plugs or replace the outlets with 3-prong ones as Drubin suggested.
Replace one outlet with a grounded duplex outlet. The use one of those inexpensive electric outlet testers with three lights (home depot/ace/lowes/....) and see if the outlet is grounded. If it isn't, the lights will show you.

why guess when you can actually find out for less than $10.
Do check to see if your wiring is in metal conduit. You can ground to the conduit. If not, do you have access to beneath your house? (Basement, crawl space..) If so, run grounding wire down and to a pipe.

Upstairs rooms that are not adjoining a bathroom wall with pipes in that wall are a big-time problem. Look to outside walls and see what piping, etc. is out there. Ground to that.
Just to state the obvious....a ground to pipe is only useful if that pipe is metalic all the way to the outside of your house.

Connecting to a plastic/non metalic pipe is useless as a ground. Just because the pipe you see is metal does not mean it's a good ground. Some houses run all their water thru a plastic filter (softener, iron, whole house,....) and if there is no all metalic path to the outside of your's not a ground.

If your water comes from a well and you have plastic pipes outside (or down the well), it's not a ground either.

Most people forget all of the above and just figure...ah a pipe, I'll connect and I now have a good ground. What you have is a connection that can potentially kill you, not a ground.
Yes, that is why you need to use a ground tester. Also, I doubt a reputable electrician would stand by the cheat that uses the skrew in the outlet.

Mine wouldn't.