I just received a brand new Thinkpad with i5 processor. If I got this right this processor is based on the Intel 64 architecture. Certain applications claim that they can run only on x86 based systems so I was wondering if this processor is backward compatible. Is 'Intel 64 architecture' a superset of x86. Can I still run those applications?
Yes that processor is backwards compatible with 32 bits applications, so you can run 64 or 32 bits applications with no issues.
Remember that you need to make sure that the motherboard or in this case the laptop itself most also supports 32 bits operating systems for certain 32 bits applications.