Some of the early versions of World of Goo released by 2D Boy can still be downloaded with the Wayback Machine.

However, be warned that these prototypes are prone to crashing. To get around this you can unlock all of the levels by editing your profile using the following video tutorial by Crazy_Fox2:

To summarize:

1. Save data is stored in the Windows Registry which can be modified with the Registry Editor.
2. Go to the "HKEY_USERS" folder, and then the folder that starts with "S-1-5-21" and ends with "-1001_Classes".
3. Profile data can be found by navigating further to "VirtualStore\MACHINE\SOFTWARE\WOW6432Node\2dboy\goo\profiles".

Crazy_Fox2 provided the following to unlock all the levels in the different versions, which you can use or modify:

rev821

1,WorldOfGoo,25,ToGIsland,0,GoingUp,8,HelpMeUp,3,Jengoo,0,JawBridge,0,EconomicDivide,4,ImpaleSticky,1,JunkInTheTrunk,9,HangLow,0,HungryHungryHills,0,FlyAwayLittleOnes,0,DrillBit2,0,Liftoff,0,DrillBit,0,TheJungle,0,Demolition,0,StraightUp,0,Juicer,0,BigRavine,0,CogInTheMachine,0,ATasteOfGoo,0,FreeTShirts,0,MissionMildlyPlausible,0,ZeArena,0,WorldOfGoo,0,b:common:-40:200:0:0:b:common:40:200:0:0:b:common:0:280:0:0:s:common:0:1:0.0500:80.0000:s:common:1:2:0.0500:80.0000:s:common:2:0:0.0500:80.0000:b:common:42:883:0:0:b:common:-58:723:0:0:b:common:-83:702:0:0:b:common:-42:874:0:0:b:common:-11:717:0:0:b:common:27:655:0:0:b:common:83:819:0:0:b:common:26:759:0:0:b:common:-7:844:0:0:b:common:-96:637:0:0:b:common:91:898:0:0:b:common:24:600:0:0:b:common:-15:875:0:0:b:Ivy:1:747:0:0:b:Ivy:-85:824:0:0:b:Ivy:-50:693:0:0:b:Ivy:-34:850:0:0:b:Ivy:-24:834:0:0:b:Ivy:-33:702:0:0:b:Ivy:67:873:0:0:b:Ivy:1:714:0:0:b:Ivy:90:883:0:0

rev601

default,ZeArena,default,22,GoingUp,HelpMeUp,Jengoo,JawBridge,EconomicDivide,ImpaleSticky,OutOfThePit,HangLow,HungryHungryHills,FlyAwayLittleOnes,DrillBit2,Liftoff,DrillBit,TheJungle,Demolition,StraightUp,Juicer,BigRavine,CogInTheMachine,ZeArena,ObjectsInSpace,RollRollRoll

rev400

default,Demolition,default,9,HangLow,OutOfThePit,GoingUp,EconomicDivide,ImpaleSticky,DrillBit,RollRollRoll,TheJungle,Demolition