Ok, so I just completed my new build. I'm using some existing parts, but new CPU, motherboard, case, and RAM.

I'm using my old 1 TB hard drive from my last machine and I haven't wiped it clean to start over. I'm running the same windows install from the previous machine. After one day of running, so far it seems quite stable. No problems whatsoever thus far. I bought a new copy of Windows 7 (the copy on my hdd came pre-installed because it was a store bought PC), but now I'm wondering if I should return and just see how the computer handles the old OS install. Am I fooling myself? Am I bound to have problems so I should just get the fresh install over with now? I'd love to save the $100 as money is a little tight these days.

Must be missing something. Why do you need a new copy if you've already got a serial for it?

A fresh install is advisable with completely new hardware, but if things are running and you have no complaints, then that seems fine.

You can totally use that OEM install of Windows from your old machine and do a fresh install. I'd suggest using a program called activation backup and restore to avoid any activation issues (calling the number Microsoft provides during activation and doing their little dance of inputting numbers and getting sent an activation code is a pain, but it also totally works just fine). Just make sure to use the beta version that has Windows 7 support.

And if you can't find your Windows product key. there's a program called Magical Jellybean Keyfinder. Download the free version and run.

Then it just becomes a matter of downloading an image of Windows 7 if you don't have a recovery disc or partition.

@AndrewB said:

A fresh install is advisable with completely new hardware, but if things are running and you have no complaints, then that seems fine.

You can totally use that OEM install of Windows from your old machine and do a fresh install. I'd suggest using a program called activation backup and restore to avoid any activation issues (calling the number Microsoft provides during activation and doing their little dance of inputting numbers and getting sent an activation code is a pain, but it also totally works just fine). Just make sure to use the beta version that has Windows 7 support.

And if you can't find your Windows product key. there's a program called Magical Jellybean Keyfinder. Download the free version and run.

Then it just becomes a matter of downloading an image of Windows 7 if you don't have a recovery disc or partition.

This makes sense. I'm kind of a noob in terms of PC building so I guess I thought my old recovery disc and all that wouldn't work to install windows on a NEW system. But this makes sense. I'll give it a shot sometime in the next couple days if I have any problems on my current install. So far the only real issue I'm running into is trying to get the new mobo to recognize my GPU.

In theory OEM windows 7 isn't allowed to be installed on a new PC but I've had it work fine. Sometimes it asks you to call support to reactivate, just say you upgraded the PC.

If you replace the MB, I recommend a full re-install to avoid any problems.

Just an update, I've been running this machine pretty hard (gaming, installing programs, photoshop, etc.) for four days now and no problems. It's totally stable, which I'm pretty surprised by because I'm still running on my old hard drive with the old Windows 7 OEM install.

If it's been running like that for several days, you should be fine (of course, always backup, no matter the circumstance...). However, it's possible the install is not optimized to your new hardware. So, it's really up to how much effort you want to put into it, but I'd personally do a fresh install with the same copy of Windows 7 (i.e. return the one you purchased and just use the same key that you already had like others recommended above). Glad to hear everything is working out, though!! It always stinks when PC builds end up in headaches (I've had many...).

The new motherboard is the thing that is going to force you to reinstall windows. If it was just a CPU, ram, gpu upgrade you would have been fine.

@dream431ca said:

If you replace the MB, I recommend a full re-install to avoid any problems.

@Nate said:

Just an update, I've been running this machine pretty hard (gaming, installing programs, photoshop, etc.) for four days now and no problems. It's totally stable, which I'm pretty surprised by because I'm still running on my old hard drive with the old Windows 7 OEM install.

Well you're in luck - I replaced my MB, ram and cpu recently and my PC wasn't even able to find the bootmgr.sys file so I clean installed. Overall it wasn't as painful as some of my previous re-installs. I've learned to keep a minimum of programs onboard so I have a pretty short list of like 10 items to reinstall.