Hi - I had the same issue, new Win7-64bit laptop & still use the Sony ICD-P620 recorder & found out that the Sony Digital Voice Recorder software is not compatible w/ Win7 64-bit. (Yaah, I know - sorta lame don't provide a compatible version.) However, Chat support was painless & quite helpful. Somewhat rudamentary but the following link has steps to at least transfer the recordings.
Grabador De Voz
Es posible memorizar hasta 25 emisoras de radio de FM en la memoria de la grabadora IC. ES 1 Pulse FM para pasar. Para descargar las instrucciones SONY ICD-P630F. Sony IC recorder icd-p630f driver - Sony ICDP630F (512 MB 2615 Hours) question. Descargar driver grabadora sony icd-p630f. Todos los drivers que necesites de Grabadoras para descargar al instante con nuestro sistema de descarga directa.
Icd Px440 Manual
The instructions are for recorders that don't have a USB cable but you can (apparently) use the same method to download your ICD-P620 files. I haven't tried it yet but I assume there are other programs, perhaps preloaded w/ yr Win7 system, that can then edit and/or convert the recordings with more sophistication, if you need it. Best of luck, here's the article from Sony Chat support.