Memory Handling Check

[Anzy]

Hi.. I'm very new to C++ and have just written 2 methods that are pretty unstable (ie. same input may or may not run correctly). My gut feeling tells me it's because of my poor memory and string management. Could someone kindly review the code and let me know if there's any obvious error? I would seriously very appreciate it. Method 1 ============

char* _LoggedInUserID;
char* _LoggedInUserName;
DWORD CALLBACK streamDisclaimer(DWORD_PTR dwCookie, LPBYTE pbBuff, LONG cb, LONG *pcb)
{
DWORD read;
CRtfStream *st = reinterpret_cast(dwCookie);
const int MAX_USER_TAG = 10;

char\* userTag = (char\*) malloc(strlen("")+1);
strncpy(userTag, "", strlen(""));
userTag\[strlen("")\] = '\\0';

size\_t displayLen = strlen(\_DlgLoggedInUserID);
if(\_DlgLoggedInUserName != NULL) displayLen += strlen(\_DlgLoggedInUserName) + 3;  	char\* displayStr = (char\*) malloc(displayLen+1);

if(\_DlgLoggedInUserName != NULL){
	sprintf(displayStr, "%s (%s)", \_DlgLoggedInUserName, \_DlgLoggedInUserID);
}else{
	sprintf(displayStr, "%s", \_DlgLoggedInUserID);
}
displayStr\[displayLen\] = '\\0';

LPBYTE tmpBuff = new BYTE\[cb + (displayLen\*MAX\_USER\_TAG)\];

ReadFile(st->fileDisclaimer.get(), tmpBuff, cb, &read, NULL);
string tmBuffStr = (char\*) tmpBuff;
size\_t iPos      = tmBuffStr.find(string(userTag), 0);

if(iPos != tmBuffStr.npos){
	int cnt = 0;
	while(iPos != tmBuffStr.npos && cnt < MAX\_USER\_TAG){
		tmBuffStr = tmBuffStr.erase(iPos, strlen(userTag));
		tmBuffStr.insert(iPos, displayStr);
		iPos = tmBuffStr.find(string(userTag), 0);
		cnt++;
	}
	int newLength = read - (strlen(userTag)\*cnt) + (displayLen\*cnt);
	strncpy((char\*)pbBuff, tmBuffStr.c\_str(), newLength);
	pbBuff\[newLength\] = '\\0';
	\*pcb = newLength;
}else{
	strncpy((char\*)pbBuff, (char\*)tmpBuff, read);
	\*pcb = read;
}

// clean up
delete \[\] userTag;
delete \[\] displayStr;

userTag    = NULL;
displayStr = NULL;
tmpBuff    = NULL;

return 0;

}

Method 2 =============

char* _DlgLoggedInUserID;
char* _DlgLoggedInUserName;

void CGina::setLoggedInUserID(PWSTR pszUserName){

// free memory dynamically allocated
delete \[\] \_LoggedInUserID;  
delete \[\] \_LoggedInUserName;

// deallocate memory that's not used
\_LoggedInUserID   = NULL;
\_LoggedInUserName = NULL;

if(pszUserName != NULL)
{
	int nstrlen = WideCharToMultiByte(CP\_ACP, 0, pszUserName, -1, NULL, 0, NULL, NULL);
	PSTR UserNameStr = (PSTR)HeapAlloc(GetProcessHeap(),0,ns