I have a Windows XP 64 bit version and all applications work as 32 bit.
I'm having difficulties running these applications.
How can I make them work as 64 bit?
The only way you'll make the applications work as 64-bit applications is to compile them as 64-bit applications. Til you do that, they'll run as 32-bit. They should work fine, but will have most of the same limitations they've always had.
There are ways to help ensure that code will be compatible with 32- and 64-bit processors. Make sure you don't do int-->pointer and pointer-->int conversions, or rely too much on the size of ints, longs, etc.
If you don't have the original code, you're kinda screwed, and will have to wait for whoever does have the code to release a 64-bit version of the app.
See this article: http://support.microsoft.com/kb/896456
From the article:
The WOW64 subsystem does not support the following programs:
Programs that are compiled for 16-bit operating systems
Kernel-mode programs that are compiled for 32-bit operating systems
The only way to make an application compiled for 32 bit execution run as a 64 bit application is to recompile the source code into a 64 bit executable.
There are too many side effects of the 32 bit to 64 bit transition to do this automatically to an app that was written only with 32 bits in mind.
Aside from getting the source and rebuilding yourself (not trivial) or having the vendor rebuild these for you, as others have suggested. And since you probably have not worked with developed based on your comments...you probably should just get Virtual Machine software (such as VMware or Microsoft's VPC, though I don't know if either provide a version for Windows XP 64-bit) and and install a 32-bit Windows on it in which to run your applications.