Build.target confusion

Development Tools IDE 1.x
1

Hi all,
A while ago I pieced together a Arduino sketch and it worked well. I bought a new laptop recently and installed the version of Arduino I originally wrote the sketch on (0017).
Now when I try to compile the sketch I get the following error:

java.io.IOException: Target platform: "null" not found.
Make sure that "build.target" in the 
preferences file points to a subdirectory of 
C:\Users\Ross\Desktop\Arduino17\arduino-0017\hardware\cores
	at processing.app.debug.Target.<init>(Target.java:49)
	at processing.app.Editor$43.run(Editor.java:1751)
	at java.awt.event.InvocationEvent.dispatch(Unknown Source)
	at java.awt.EventQueue.dispatchEvent(Unknown Source)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
	at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
	at java.awt.EventDispatchThread.run(Unknown Source)

When I go to the preferences file there is no build.target. There is however a

# temporary build path, normally this goes into the default
# "temp" folder for that platform (as defined by java)
# but this can be used to set a specific file in case of problems
#build.path=build

and a

# may be useful when attempting to debug the preprocessor
preproc.save_build_files=false

Pls help, I'm really lost!

2

I should add that is not an error as such that comes up, however it gets stuck compiling and that above feedback shows.

3

Why don't you use the latest version of the IDE?

4

I wanted to confirm everything was working in the IDE I had written the code in, before updating.

5

I have now updated to 1.0.1. just need to update the old libraries and the code. Busy day tomorrow!