I'm switching to iMac after 15 years with PC. I have a ton of software on my HD. Us there a way to scan my PC to detect all the programs that are compatible with Mac ? To do it manually would be a huge hassle. Or maybe the best way, just forget and to check only the major brands ? Thanks!

PC Software is entirely different, you will have to start afresh. Most of your saved Data should have Mac Software to read it though.

Chances are if you have a program on your PC there's a Mac equivalent available. But in the case of commercial applications you may have to buy the software again, only in Mac OS format. Although there may be free alternatives also. For example, MS Office, you can get a Mac version of that. But you'd need to buy it even if you already own the PC version. However you could instead use OpenOffice which is opensource (so free) but is also available for OS X, and will open pretty much all MS Office documents.

If you still have the installation media or packages, you don't have to buy all new software. If you're buying a new Mac with an x86 INTEL processor, you can dual-boot Mac and a Windows OS of your choice using a free tool called 'Boot-Camp', or run a virtual session of Windows called "Parallels Desktop"($75) that will run, on demand, within your Apple environment. Both are very easy to set up. If you've truly been on the Windows platform for 15yrs, or long enough to accumulate a wealth of applications; then trust me and don't give it up cold turkey. You'll only be disappointed. Operating systems aren't gangs or political affiliations, folks. You don't have to stick to one exclusively.