(2-part post):
If you've really got LOTS of negatives and slides, it might be worth investing in a dedicated film scanner. Not so long ago, most film scanners cost over �1000 but there are now more reasonably priced models available:
For near-professional quality, the Nikon Coolscan V has a good specification but it will set you back about �500:
http://www.jessops.com/Store/s46854/0/Scanners /Nikon/Coolscan-V-Film-Scanner/details.aspx?&I sSearch=y&pageindex=1&comp=y
The Plustek 7200i, at less than half the price of the Nikon model, theoretically offers a higher resolution but the quoted figures for scanner resolutions can be misleading as they often use 'interpolated' figures:
http://www.jessops.com/Store/s36227/0/Scanners /Plustek/7200i-Film-Scanner/details.aspx?&IsSe arch=y&pageindex=1&comp=y
At �170, the Plustek OpticFilm 7300 seems even better value:
http://www.jessops.com/Store/s66948/0/Scanners /Plustek/OpticFilm-7300-Film-Scanner/details.a spx?&IsSearch=y&pageindex=1&comp=y
The Veho scanner, at �100, is a possible budget solution. It's 'minus' point is that the resolution isn't any better than that offered by cheaper flat bed scanners. It's 'plus' point is that, if you've got lots of slides and negs to scan, it will be far quicker to use: