i converted a traditional ira to a roth ira in 1998 and planned on paying the taxes over 4 years. this year in doing my taxes i see that i have made 150,000 and i was wondering if that disqualifies me from converting?

As long as your AGI was below the threshhold in 1998, the year in which you converted the IRA, you're fine. The conversion was actually made totally in 1998. All you're doing is spreading the tax on that conversion over 4 years.

Hope this helps.