How can I use my computer while mining with cgminer?

I'm currently mining Bitcoins and Litecoins, (AMD 5850)
for Bitcoins I use 'GUIMiner' using 'OpenCL miner',
for Litecoins I use 'GUIMiner-scrypt' using 'cgminer'.

Now, for Bitcoins I just add the flags "-v -w128 -f 60" and it works extremely fast even when I play BF3 and nothing shatters (If I play heavy graphics games it will go down to ~150Mha/s tops, and when I finish playing it jumps back to ~300Mah/s), the computer works flawlessly,

but for Litecoins whenever I use the flag "-I d" it goes down to 10% of it's power (from 325Kha/s to 30-20Kha/s) even when I just look at the computer!

So again, my question is, is there any way to have the same experience with performance while using the computer with cgminer?
Or, alternatively, is there anyway I can mine Litecoins with GPU, using the computer at the same time and still have maximum performance as I just demonstrated that I have with OpenCL miner?

thanks for the help, hope I gave all the details necessary!