hi woody
you can install windows 7 from a usb key... and theres a excellent and easy to understand guide at http://www.intowindows.com/how-to-install-windows-7vista-from-usb-drive-detailed-100-working-guide/
however you need a mediocre knowledge of windows and command prompts to carry out this installation... but it should be within most peoples capabilitys
on the other hand you can get a dvd-rom/cd-rw drive for just £7-99 from http://www.ebuyer.com/product/129233 ... the "Samsung SH-D163C 16x DVD-ROM CD-R SATA Optical Drive " is a o.e.m (original equipment manufactuer ) version so it comes with nothing else... just the drive... that said i purchased one of these a few months ago for a build and i got "nero 8" bundled with it.... i think its luck of the draw...
this is a sata drive so you need a spare sata port... however you can get a "ide" version from http://www.ebuyer.com/product/220991 ... the "Sony Optiarc DDU1678A 18x DVD-ROM IDE Optical Drive" is slightly better than the samsung model( hence the price ) but this uses a ide(pata) connection....
to check what you have compare these images to the back of your broken drive
sata ( http://serialstoragewire.net/images/articles/it24fig1.jpg )
ide/pata ( http://www.mysuperpc.com/build_your_own_computer/dvd_rw_ribbon_cable_connection_cr.jpg )
as you can see it wont cost any more than £11 to replace your dvd-rom .. infact you can get a full dvdrw/cdrw drive from http://www.ebuyer.com/product/237048 ... for just £12-99 ... and thats a retail box... so you will get the drive,spare bezels(fascia,s),cables and a copy of nero 9... not bad for £12-99 !
this covers all area,s and even supports dvd-ram which is what recordable dvd players use... so this is seriously worth considering... i recommend this especially when you consider what your getting with it !
i hope this helps,any problems let me know
good luck woody !