I assume that you are getting the dialog that says "Error! Too many peaks." when you are fitting from the menu, Analysis:Fit Multi-peaks.You can use the Nonlinear Curve Fitter to fit multiple peaks. In the Advanced Mode of the fitter, select Options:Replicas, to set the number of peaks.
Origin's menu fitting routines are 'quick fits', but do not allow the user control over the fitting session like the NLSF does.
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Laurie
Microcal Technical Support