Briefly, find computer management, through control panel>system and go to disc management.
You should be able to see how your drive is partitioned there.
If it shows Windows and some Unallocated Space or another drive then you'll need to erase the contents of the “other” partition and extend your new Windows partition to make use of the bit you've just cleaned.
It sounds like you didn't re-format your drive before you re-installed windows.
AND DON'T KEEP YOUR MUSIC ON THE SAME DRIVE AS YOUR OPERATING SYSTEM!
It's just asking to lose all your music files. Buy an external drive, two in fact, one for backup and just keep the bare bones operating system on the computer.
Then go to my thread on moving from Windows to Linux and follow the instruction for partition management.
Just remember, if you stuff up with the partitioner you can just reinstall windows and format the complete drive.
Single spur balanced Mains. Self built music server with 3 seperate linear PSU, Intel i5, 16 GB RAM no hard drive (various Linux OS). Benchmark Dac2 HGC, single ended XLR interconnects/Belkin cable. Exposure 21RC Pre, Super 18 Power (recap & modified). Modded World Audio HD83 HP amp. Hand built Monitors with external crossovers , Volt 250 bass & ABR, Scanspeak 13M8621 Mid & Scanspeak D2905/9300 Hi. HD595 & Beyer 880 (600 ohm) cans.
The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts.
-Bertrand Russel
John.