Lover Spy software, will let you see exactly what your partner (or for that matter anyone else) is doing on their computer simply by sending them an e-card. Quoting from their site:
Through our service, you compose and send your lover a normal-looking "Greeting Card" saying "I Love you" or a similar message. Because the e-mail appears to be a regular greeting card, the recipient will open the e-card and LoverSpy will be automatically and silently installed!.... It records and sends you all e-mails they view, including Hotmail, Yahoo, and Outlook emails.....All the Passwords they type into their web browser are also recorded and sent to you. Every single Chat conversation they have on the internet. In fact, every Key stroke they type into the computer is recorded and sent to you in an organized report. Every single web site they visit....EXACT copies of every Hotmail e-mail viewed, Yahoo, Excite, AOL, and even Outlook emails. All these e-mails are Forwarded to you in the background, in real-time! After they read their email, you will have a copy of it - seconds later.
Are they mad? CNet reckons its illegal, which is absolutely right. It's also a thousand times more likely to be used by stalkers than wronged partners. In the meantime...I'll be ignoring all those e-cards I get from people telling me they love me.