Burned out power supplies in the Acer Aspire X1700 Desktop series seems to be common.
The power supply unit is not a standard form factor. You cannot just go to Newegg.com and grab one.
The power supply unit is most likely the Delta Electronics, Inc. DPS-220UB A
Output: 220 Watts
Dimensions: 7.87" (L) x 3.58" (W) x 2.126" (H)
Try here at Ascendtech Inc.