Yeah, get a 2.5" to 3.5" adapter. You can also get 3.5" to 5.25" adapters if you need to get a new hard drive or 3.5" floppy drive, but you only have 5.25" bays left.
(Comon, what kind of PC manufacturer would give you more 5.25" bays than 3.5" inch bays?.....well mine did...grrr)