I just bought a zotac GeForce gt 640 to replace my broken radeon hd 4850 and it keeps makeing these small streaks across the screen off and on no matter what I'm doing. I updated the drivers and that didn't help. So is the card bad? I'm running windows 8 32bit.
RAIDMAX SMILODON ATX-612WBP Black 1.0mm SECC Steel ATX Mid Tower Foldout MB Computer Case With 500W Power Supply
SAMSUNG 22X DVD±R DVD Burner Black SATA Model SH-S223Q LightScribe Support - OEM
Creative Sound Blaster Audigy SE 7.1 Channels PCI Interface Sound Card
Logitech MX 518 8 Buttons 1 x Wheel USB Wired Optical Gaming Mouse
Intel Core 2 Duo E8400 Wolfdale 3.0GHz LGA 775 65W Dual-Core Processor BX80570E8400
SAPPHIRE 100245L Radeon HD 4850 512MB 256-bit GDDR3 PCI Express 2.0 x16 HDCP Ready CrossFireX Support Video Card
ASUS P5Q Pro LGA 775 Intel P45 ATX Intel Motherboard
Logitech G11 Gaming Keyboard
Western Digital WD Blue WD5000AAKS 500GB 7200 RPM SATA 3.0Gb/s 3.5" Internal Hard Drive -Bare Drive
OCZ Platinum 2GB (2 x 1GB) 240-Pin DDR2 SDRAM DDR2 1066 (PC2 8500) Dual Channel Kit Desktop Memory Model OCZ2N10662GK
Your momentary fix is normal because when you uninstall drivers the display device switches to an integrated display known as the standard VGA adapter. Then once you reinstall drivers the card becomes the main display device again.
If the streaks appear with the card and not the vga adapter it's time to RMA.
EDIT: about your safe mode issue, then your drivers may be installed wrong, uninstall the drivers through catalyst/control panel, then use CCleaner to remove residual traces of the driver, then install again.