will uninstalling windows 7 effect windows 8

Make your Sony Recovery disks if you think you might need to ever go back to the factory install, mainly if you're under warranty and they require it to ship back for service or you might want to sell it in that condition.

However we've always been able to resolve any issues with Sony hardware on a Clean Reinstall - Factory OEM Windows 7 which is discussed in the Special Note for Vaio Owners at the end of so if you're like the vast majority we've helped with this here you will never want to go back to factory bloatware install yourself.

So it's up to you if you want to keep the Recovery partition after you make the disks. It may not run from boot after a Clean Reinstall, however if the disks ever failed we can help you Boot Recovery Partition using EasyBCD from the OS. I wipe Recovery partitions on my machines because I want nothing to do with that mess.

Once you decide and have done your backup and other preparations as compiled in Clean Reinstall - Factory OEM Windows 7, boot the installer, referring to the illustrated install steps in Clean Install Windows 7 when you get to Steps 7 and 8 use the Drive Options to delete System Reserved, C, and if you want Recovery partitions. If you do not touch the D, E and F partitions then nothing on them (including WIndows 8) will be affected.

In the space you've deleted using the Drive Options, create a new Install partition. It may prompt you that it wants to create a new System Reserved partition which is fine. Highlight the new install partition to Format and then click Next.

If things go as expected it should add Windows 8 to a Dual Boot menu, if not install EasyBCD to Win7 to add 8. Windows 8 cannot now boot itself since its System boot files cannot be written to a Logical partition until it is converted to Primary and marked Active. However since you want a Dual Boot then Win7 will be booting Win8 anyway.

Be sure to follow the Clean Reinstall - Factory OEM Windows 7 steps closely because you will get and keep a perfect Win7 install to the exact extent you do. Put your network driver in the backup in case it's not provided during install so you can install it to get online quickly to enable Automatically deliver drivers via Windows Update (Step 3) then run all rounds of Important and Optional WIndows Updates, with reboots, until there are no more. This will deliver most drivers and critical Performance and Security Updates. Any drivers still missing after this in Device Manager can be imported from the Vaio Support Downloads webpage for your exact model.

Wait to see if you need any of the Vaio software for important functions you rely upon on the laptop, otherwise avoid it to enjoy Win7 for the first time on that machine in its native perfect state.