You also have a potential buffer overflow by passing 101 as the buffer size parameter to istream::getline, which should be 100, the size of your buffers. Also, if you use code tags instead of quote tags you can include the whitespace so reading the code isn't painful.
This is almost ridiculously easy if you use STL strings and vectors as you can sort everything with one statement eg:
Code:
string s;
vector<string> v;
while (getline(inFile, s))
v.push_back(s);
while (getline(inFile2, s))
v.push_back(s);
sort(v.begin(), v.end());
for (unsigned i = 0; i < v.size(); ++i)
outFile << v[i] << endl;
#include <algorithm>, <string>, and <vector> in addition.