Open the case, look at the upper left-hand corner of your pc case, and look around for some box, some rectangular box, one like this:
and look for a label that says something like this: 350W or something along those lines.
yeah it looks like that one but not all neon colored. if it is only a 350 watt PSU it is highly recommended that you get a 400 watt and up to run a 6600 and 6800. but take it from me, replacing a PSU with Dell's is really weird. i had to rip the metal to get the plug area in and i dont think it will be any different with yours. ill take a picture in a second.
Here's the power listed on the DeLL website for her model:
Input Voltage: 100 to 120 V at 60Hz, 200 to 240V at 50Hz
Output Wattage: 305W maximum continuous
Heat Dissipation: 560.5 BTU/hour
Backup Battery: 3.0 V CR2032 coin cell
That's not nearly enough, huh? The PSU only puts out 305 watts. That seems way too little, even for the base specs of the system. Do we maybe overestimate wattage here by a good deal?