It's not too late to get your hands on the cheapest Windows 7 edition for students. The official Ultimate steal deal direct from Microsoft that offered Windows 7 Home Premium for £39.95, has ended although you can still buy Office Ultimate 2007 for £38.95.
In September last year, Microsoft offered Windows 7 Professional for as little as £30. The offer ended on the 3 January.
However, Pugh is now stocking two Windows 7 versions (Professional & Ultimate), both available for discounted prices but only as 32-bit or 64-bit upgrades, not full versions. The professional version costs £33.37 while the Ultimate version costs £63.45.
According to some sources, unlike other companies like Adobe, no formal checks are performed as long as you have a valid .ac.uk email address.
Note that students will only be allowed one software license to avoid fraudulent applications and Microsoft will ship a DVD and the serial key directly to your address.
There's also the fact that an acceptable version of Windows will have to be present for the upgrade to be legally valid.
Not having a genuine version of Windows WON'T stop you from installing Windows 7 (you can do a custom or clean install) but then you might just as well download the OS from Bit torrent and run a key generator.
If your computer did not come with any genuine operating system, you might want to buy an old version of Windows from a reputable source.
You can get Microsoft Windows Vista Home Basic from Computer Exchange from £55 including delivery although that would boost the price of the upgrade to nearly £90.
Alternatively, you can catch Windows 7 Professional for students from Microsoft for £70 only.
You just need to Enter your university/college email address to see if you qualify and receive an email from Microsoft that will allow you to purchase. Note that the service is provided by Digitalriver and will work even if you are not installing it on top of another OS.