If you did an Upgrade rather than a Clean Install (which is what I'm assuming from the way you've worded the post) than all your old files are kept in a folder called "Windows.Old" which is located in your C: . It is safe to delete this folder but just make sure none of your personal files are in it before you do.. If there are any in it than you simply copy them to a new location and than the file can safely be deleted.. Doing so should free up a good chunk of realestate on your HDD too as this file can be quite large.. 
I'd also recommend doing a check in "Device Manager" to make sure that 7 has installed all your drivers.. If there are any drivers missing then you'll see a yellow exclamation mark beside whichever device is missing the driver.. 
Upgrading isn't really the recommended way to install a BETA or RC version of an OS.. but to each his own..
A clean install would have avoided this problem..
Operating System Windows 7 Ultimate 64- Bit Edition
Computer Type Custom Build 6 of 6
CPU Type and Speed AMD Phenom II X4 965 (3.4GHZ) 4000MHz HT Quad-Core Socket AM3
Motherboard Chipset Asus Crosshair III Formula AMD 790FX Socket AM3
System Memory Type Corsair TR3X6G1600C8D Dominator - DDR3-1600:PC3 -12800 - 6GB - Non-ECC Unbuffered 240-Pin DIMM
Video Card Type and Speed Sapphire Radeon HD 5870 1GB PCI-Express (2.0)
Computer Monitor Samsung SyncMaster P2350 23" FULL 1080p HD LCD Monitor
Hard Drive (2) WD VelociRaptor 300GB 10000RPM 16MB Buffer: (2) WD Caviar 1.5TB "IntelliPower" 64MB Buffer
Optical Drives (2) LG 22x Super Multi Drives (SATA II) - Both with Lightscribe
Network Adapter Asus Crosshair III Formula Gigabit Ethernet Adapter
Anti-virus Software AVG Free Edition 9.0
Computer Skill Level Self-Taught Expert
Windows Experience Index 7.2