If you really, really insist on hanging on to Abc2Win rather than moving to abcExplorer, and it won't work under Compatibility Mode as described by JohnInKansas, you might want to investigate XP Mode - http://www.microsoft.com/windows/virtual-pc/download.aspx. It's official Microsoft software (it's a slightly-more-consumer-friendly implementation of Virtual PC) and it's free.

It takes a while to set up (it isn't that complicated, just set aside an hour or so and you do need to do things exactly in the order specified on the above page); and then it takes longer than usual to launch the actual program once you've installed it in XP Mode - but it seems to work pretty well for running older programs that just won't play with either Win7 per se or with the 64-bit version in particular.

But seriously, ditch Abc2Win and get onto abcExplorer - abc2Win was brilliant in its day, but that day is long gone now there is abcExplorer to be an excellent free equivalent that doesn't produce broken abc.