Launcher doesn't allow more than 1 GB RAM

[Kyren_]

Launcher Version: Launcher Build 253

Operating System: Windows 7 64 Bit

Java Version: Version 7 Update 25

Antivirus Program: Norton Antivirus, Comodo Firewall

Description of Problem:

I'm posting this on behalf of a friend who isn't that fluent in English. His minecraft starts lagging after approximately 5 minutes, on vanilla and on modded minecraft. We ignored it on vanilla and switched to Pixelmon, and the lagging continues here. He's even lagging when the RAM usage depicted by F3 is low, some 13% and such numbers.

We wanted to try to allocate more RAM to his minecraft, because currently it uses 1 GB. We tried it over the Techniclauncher, but it doesn't allow more than 1 GB, even after updating Java (and prior deinstallation of all old java versions) and redownloading and installing the Launcher.

I suppose Minecraft uses his graphic cards RAM, but it seems to be to little in this case. Is there any way we can allocate more RAM over the launcher or trick the launcher in allowin more than one GB?

His system specs:

TypOctalCore AMD FX-8320, 3700 MHz (18.5 x 200)

NVIDIA GeForce GTX 650 Ti (1 GB)

DDR3 4GB 1333 Elixir/Team RAM , x2

Error Messages:

Error Log: