Windows 7 not starting

I have an IMac 27", I partitioned he hard drive installed bootcamp and Windows 7 and it works most of he time. Now what worries me is the fact that every now and then when I go to boot from the window side it just freezes on the partition selection screen, this has happen several time over the last 6 months or so the first time I contacted Apple they said talk to Microsoft which I did and they said re-format and re-install windows 7 ( And that was their first option no fixes just wipe the lot and start again) .

Second time around I re-booted it maybe 8-10 time and it started to work ran a load to tests on the hardware / software and everything came back okay this has happened 3-4 time and it always worries me, there's nothing I cannot re-download but it's a lot a lot of work that I'd rather not do. Does anyone have any idea's on how to avoid this kind of problem or should I just accept that the fact the window's is just a bit ****!.

NB.
I don't have enough space to back up the windows side as well as the Mac side atm

Windows 7 freezing is almost always indicative of a video driver problem. Try updating the video drivers. And, you really haven't given us much information about your system to go on.

As requested abit more info:
Model Name: iMac
Model Identifier: iMac11,3
Processor Name: Intel Core i7
Processor Speed: 2.93 GHz
Number of Processors: 1
Total Number of Cores: 4
L2 Cache (per Core): 256 KB
L3 Cache: 8 MB
Memory: 8 GB
Processor Interconnect Speed: 4.8 GT/s
Boot ROM Version: IM112.0057.B00
SMC Version (system): 1.59f2

Graphics:
Chipset Model: ATI Radeon HD 5750
Type: GPU
Bus: PCIe
PCIe Lane Width: x16
VRAM (Total): 1024 MB
Vendor: ATI (0x1002)
Device ID: 0x68a1
Revision ID: 0x0000
ROM Revision: 113-B9710C-238
EFI Driver Version: 01.00.417
Displays:
iMac:
Resolution: 2560 x 1440
Pixel Depth: 32-Bit Color (ARGB8888)
Main Display: Yes
Mirror: Off
Online: Yes
Built-In: Yes
Connection Type: DisplayPort

If I get it to boot I'll update the drivers and post the results

Thanks for posting your specs. That helps us to help you. Take note that your machine is a 2010 iMac which requires a special driver download from Apple. The 2010 and 2011 iMacs need the driver download (and burned to disk) before Boot Camp can proceed with the installation and creation of the partition for Windows 7. Did you download the drivers from Apple when you initially set it up?

I upgraded using

Boot Camp Software Update 3.1 for Windows 64 bit

Which is Boot Camp Software Update 3.1 for Windows 64 bit

That update has nothing to do with video drivers nor does it include any. It's primarily for the wireless keyboard and trackpad functions in Windows 7.

Fixed

Got it all back up and running I rang Apple but they had nothing to offer since the apple side worked fine they just said it was a Microsoft issue.
But I tried removing all other external hard drives, Scanners, Printers etc and it now works fine I couldn't tell you what it was exactly but I believe it was external Hard Drives causing the problem.

thank your help all the same

Thanks for posting back. It probably was one of your external hard drives. As long as they're attached when Windows starts, Windows will try to enumerate them as it does with all other peripherals. Strange though that it froze completely.