First, you must be willing to accept the fact that you may not be able to locate and install a video driver for that laptop. Why? The ThinkpadR51 was made at least 9 years ago. Yes, I realize that isn't all that important to you, since you wish to use Windows 7 on it, but the fact remains that laptop manufacturers would prefer you purchase a new laptop, rather than to keep installing new Operating Systems on it to avoid the purchase of new equipment. Thus, they do cease to release updated hardware drivers for the newer Operating Systems. They are in the business of selling laptops, not keeping their old ones updated. I know that doesn't sound nice, but there it is.
Now. Lenovo does list Windows Vista drivers as being available, and that is the most recent OS they provide drivers for. If you look through that list of drivers, there is nothing listed for Video however. You must look back through the Windows XP drivers to find downloadable drivers. And, there are two possibilities for that model; ATI Mobility Radeon FireGL series, and Intel 825/855 series. Now, if you follow the link there for ATI Radeon, you are taken to a strange page that doesn't seem to actually have a download, and instead talks about how the installer might turn up some odd error or incompatibility message. That's because ATI/AMD didn't make drivers for Windows 7 for that chipset. Yes. ATI/AMD doesn't support Windows 7 for that video chipset. Feel free to start from this link here and choose the options for Notebook, FireGL series, All FireGL Products, and pick the OS you would like to use.
I went into the detail about the ATI/AMD drivers so you would have a better idea of what you are up against. In actuality, this...
... indicates you have an Intel 825/855 video chipset in that laptop. Now, Intel does have an updated INF file you can download (the link I had provided above), but actually also doesn't support Windows 7 for that chipset, as you can read here from Intel.
Windows 7 OS drivers are not available for the older Intel® 810, 815, 845, 852, 855, or 865 Chipsets or Intel® 910 or 915 Express Chipsets. But, your integrated graphics controller can support Windows 7 OS by using XPDM drivers.
XPDM drivers you say? Just tell me where to get them you ask?
Intel generic versions of the XPDM drivers are available on the Intel Download Center. These drivers are listed under the Intel graphics controller product and the Windows XP operating system.
This would be the page for that video chipset from Intel, and what they have available for download. I'm not saying you will definitely find what you are looking for to make it work, I am just saying that if it is out there, this is where it is. I refer you back to my initial paragraph. You may have to accept that Windows 7 is not going to be the Operating System for that laptop. You quite possibly will have to go with Linux... might I suggest Linux Mint?