HOW TO DUAL BOOT W540 with windows 8.1 / 7

Question

I got my W540 recently with windows 8.1 pro on it. but as all engineers worst nightmare windows 8 has hard time with engineering softwares (for my case TIA Portal for  PLC programming software which only support windows 7). so i need to have a windows 7. i prefer to keep my windows 8 and have dual boot system with windows 7 added. But i can't install windows 7. initially due to disk type (GPT), then i changed it to MBR without losing my files (which only was possible if i had deleted the recovery partition- now my recovery is on my flash drive). But there are already 4 partitions on the system (1 for C: drive and 3 for recovery and system files which came originally with the product) , how can i install a windows 7? i can't add another partition because that makes my disk a Dynamic disk (which i don't really know what is). all in all, i really need windows 7 on my system ASAP.  If anyone know how to fix this please reply. Thanks guys.
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Answer 1

You are limited to four PRIMARY partitions on an MBR disk.
But other than the "active" partition (i.e. the small 100MB "system reserved" partition where Boot Manager is placed from doing a cold Windows install on an empty drive, or the 1.4GB equivalent Boot Manager partition that Lenovo provides along with other tools and utilities), all other partitions on the drive can be "logical".  They are not required to be PRIMARY, although Lenovo delivers its partitions that way.  But you can change that.
You can have up to 120 LOGICAL partitions on a drive (all of which live inside an originally PRIMARY partition which gets converted to an "extended partition" which houses all of the logical partitions.  So if you have at least one logical partition (and thus have to give up one primary partition in order to build that required "extended partitions"), that means you can have up to three remaining primary partitions and up to 120 logical partitions... all on an MBR disk.  No "dynamic", and no GPT.
Yes, that means even the Windows system partition itself (i.e. "C") can be on a LOGICAL partition.  It's only that one "active" partition (where the BIOS goes to find Boot Manager and its menu, and kick off the rest of the system boot process) which truly must be PRIMARY.  That's the only requirement.
So, if you want to use MiniTool's Partition Wizard to carve out sufficient free space for your second Windows 7 partition (by shrinking your existing Win8 partition), you can create one or more logical partitions inside that new free space, and do the Win7 install to one of those empty logical partitions.  You can then use a second logical partition in that same free space for "data", if you want.
Note that Partition Wizard can even convert one of your existing primary partitions to logical (i.e. convert it to an "extended partition", inside of which will be then be the original primary partition now converted to logical).  You can then shrink or move/resize the partitions on the drive (both primary and logical) however you want, to perhaps make room for additional "logical" partitions inside of that now present "extended partition" which can hold up to 120.  You can even convert ALL of your primary partitions except for the one "active" partition (which MUST BE PRIMARY) to logical partitions, which gives you maximum flexibility in having even more than just two bootable OS's along with one or more data partitions, etc., up to 120 logical partitions... plus the one "active" primary Boot Manager "system reserved" partition which must be kept.