I'm not sure what guide you're following but this is what I have done.
1. Make an account on
https://lc.ozcoin.net/ (or any litecoin pool)
2. Create a new worker on
https://lc.ozcoin.net/content/workers3. Download reaper
http://wiki.solidcoin.info/wiki/Reaper#Download version 13.
4. Extract the zip anywhere
5. Open litecoin.conf and reaper.conf
litecoin.conf should look like this
host newlc.ozco.in
port 9332
user name.1
pass 1
protocol litecoin
worksize 256
aggression 12
threads_per_gpu 1
sharethreads 18
lookup_gap 2
gpu_thread_concurrency 6144
reaper.conf should look like this.
kernel reaper.cl
save_binaries yes
enable_graceful_shutdown no
long_polling yes
mine litecoin
6. After you saved those run reaper.exe
If it does not crash consider raising the aggression in litecoin.conf