To check ur gpu temp, b4 opening the game right click on desktop and go into ur vid card settings and go to temp. Then go into ur game. Now u can either switch screens by holding alt and pressing tab, or ctrl esc as stated above or quit the game. The first screen that pops up is ur temp settings so u can see how hot the GPU is running, but yes it does cool down very quickly so thats why its best to have ur settings window open already.
My MSI card runs games at 55C and thats when its OC'd to 550/1.14. I never see purple spots. Money_man, maybe ur settings are too high.
AMD Athlon 64 3500+ [939 Socket] W/ ASUS "A8N-SLI Premium" (OC'd @2.4ghz) | 560W Silverstone Spider PSU | Kingston 1024 MB [512MB X2] DDR-400 PC3200 Memory | Dual MSI Nvidia GeForce 6600GT 128MB DDR3 128-bit PCIe @555/1111 in SLI | Samsung 19" LCD 930B (8ms) | Western Digital 200 GB SATA II (x2) | LG Dual Format/Double Layer 16X DVD±R/±RW + CD-R/RW Drive